What's the best small modular reactor company for new clean baseload power?

If your goal is new, clean, reliable baseload power—not merely the most interesting reactor design—I’d put GE Vernova / GE Vernova Hitachi at #1 today, with its BWRX-300.

The reason is simple: deployment risk matters more than theoretical reactor performance.

My ranking for clean baseload

Why I favor BWRX-300

1. It is actually being built. The first BWRX-300 is under construction at Ontario Power Generation's Darlington site. The Canadian Nuclear Safety Commission issued the construction licence in April 2025, and OPG reported in 2026 that the project had reached major construction milestones, including installation of the 900+ tonne reactor-building basemat.

That's a huge distinction. A lot of SMR companies have excellent engineering presentations; very few have a commercial reactor being physically constructed.

2. It's conventional nuclear technology rather than a bet on an entirely new fuel cycle. BWRX-300 is a simplified boiling-water reactor using established nuclear fuel and components. OPG specifically cited technological readiness, licensability, safety, environmental impact, economic potential and cost in selecting it.

3. It scales nicely for a utility. One reactor is about 300 MW, while four planned units at Darlington would provide 1.2 GW. That's much more useful for replacing large fossil-fuel generation than a 20–50 MW microreactor.

4. It has a potentially repeatable fleet model. The real economic prize isn't one SMR. It's building dozens of essentially identical reactors. BWRX-300 has potential deployments being pursued beyond Darlington, including the U.S., Poland and other markets.

The big caveat

I wouldn't call BWRX-300 proven economically yet.

Darlington is still a first-of-a-kind project, and first nuclear projects have historically been vulnerable to cost overruns and schedule delays. The claim that subsequent units can be built much faster and cheaper remains something that needs to be demonstrated in practice.

That's why I would distinguish:

• Best SMR for actually adding baseload capacity now: BWRX-300
• Most interesting next-generation reactor: TerraPower Natrium
• Most interesting European contender: Rolls-Royce SMR
• Highest-risk/highest-upside investment story: companies such as Oklo

TerraPower is particularly interesting because its Natrium reactor received a U.S. construction permit in March 2026 and targets commercial operation in 2031. Reuters But it is a more technologically ambitious system, so I'd give BWRX-300 the edge for near-term deployment certainty.

If you're thinking specifically about Ontario/Canada

Then the answer becomes even more strongly GE Vernova Hitachi.

Ontario has already committed to the BWRX-300 at Darlington, the project is under construction, and the federal government describes it as a project intended to establish Canada as the first G7 country with an operational SMR.

So if you asked me:

"If I were a utility in 2026 and wanted to add 300–1,200 MW of zero/low-carbon firm generation with the lowest plausible technology risk, which SMR developer would I call first?" GE Vernova Hitachi / BWRX-300 would be my answer.

If you're asking this from an investment perspective rather than a utility procurement perspective, that's a different ranking—because the best reactor company and the best stock can be very different things.

I wouldn't call BWRX-300 proven economically yet.

No single company can be definitively labeled the absolute best because the "best" choice depends on whether you prioritize immediate regulatory readiness or cutting-edge advanced technology. However, five frontrunners dominate the small modular reactor (SMR) space for clean, reliable baseload power, each excelling in distinct areas:

Top SMR Companies and Their Core Advantages

• NuScale Power : Best for regulatory readiness . It is currently the only developer with an SMR design certified by the U.S. Nuclear Regulatory Commission (NRC). Its light-water VOYGR plants utilize scaled-down, traditional nuclear technology, making them the closest to commercial deployment.
• GE Hitachi Nuclear Energy : Best for grid-scale compatibility . Its BWRX-300 is a 300 MW boiling water reactor heavily favored by major utilities due to its design simplicity and reliance on proven operational mechanisms. It has major deployment backing in Canada, the U.S., and parts of Europe.
• TerraPower : Best for next-generation efficiency and corporate backing . Funded largely by Bill Gates, the company is building its flagship "Natrium" sodium-cooled fast reactor plant in Wyoming. It features an integrated molten salt energy storage system to easily ramp power up and down.
• X-energy : Best for industrial applications . Utilizing high-temperature gas-cooled technology (Xe-100) and proprietary TRISO pebble fuel, its reactors are virtually meltdown-proof. This design excels at producing both high-temperature steam for heavy industry and steady electricity.
• Kairos Power : Best for tech-sector momentum . Utilizing fluoride salt-cooled high-temperature tech, Kairos recently broke ground on its Hermes demonstration reactor. It is notable for signing a major deal to power Google's data centers.

Direct Comparison of Leading SMR Developers

What to Consider When Choosing an SMR Partner

When evaluating these companies for baseload clean energy, you must balance three critical vectors:

Are you looking at these companies from an investment perspective , or are you evaluating SMRs for a specific commercial utility/industrial project ? Let me know so I can provide more relevant timeline or economic data.

If your goal is new, clean, 24/7 baseload power, my top pick today is GE Vernova Hitachi’s BWRX-300.

My ranking for a utility/developer

1. GE Vernova Hitachi — BWRX-300 🥇

• 300 MWe per reactor
• Conventional light-water technology derived from GE’s boiling-water reactor experience.
• Most important advantage: it is actually under construction at Darlington in Ontario, rather than being purely a licensing or demonstration project. GE says commercial operation is targeted for 2030.
• There is also substantial U.S. momentum: the DOE says a U.S.-Japan initiative targets 3 GW of BWRX-300 deployment in Tennessee and Alabama.
• My view: best combination of technology maturity, scale, regulatory path, supply chain and repeatability.

2. TerraPower — Natrium 🥈

• 345 MWe, with molten-salt storage allowing output to rise to roughly 500 MWe.
• Much more technologically ambitious than BWRX-300.
• The big milestone is that the NRC issued its construction permit in March 2026, and nuclear construction began in Wyoming in April.
• My view: potentially the most attractive long-term technology, particularly if you value load-following and integration with renewables. But it carries considerably more first-of-a-kind technology risk.

3. X-energy — Xe-100

• 80 MWe/module, designed to be deployed in four-reactor groups (~320 MWe).
• High-temperature gas reactor using TRISO fuel.
• Very interesting for industrial heat as well as electricity.
• My view: one of the strongest advanced-reactor bets, but further behind BWRX-300 on actual commercial deployment.

4. Rolls-Royce SMR

• Roughly 470 MWe, so technically it's toward the large end of the SMR category.
• Conventional PWR architecture is a significant advantage for regulatory and operational familiarity.
• It has secured serious UK/European backing and projects.
• My view: extremely credible, particularly for Europe, but less compelling for a U.S. developer than BWRX-300 today.

5. NuScale

• 77 MWe/module, with multiple modules combined into larger plants.
• It has a major regulatory advantage: NuScale's design has received U.S. NRC approval.
• But its commercial-development history has been much less convincing than its licensing history.
• My view: impressive regulatory achievement, but I wouldn't make it my first choice for a new baseload project today.

The key distinction

I'd separate "best reactor technology" from "best company to bet a new power plant on."

For the latter, I'd currently choose:

GE Vernova Hitachi / BWRX-300 > TerraPower / Natrium > X-energy / Xe-100 > Rolls-Royce SMR > NuScale

The reason is simple: nuclear economics are dominated by execution risk. A theoretically superior reactor that takes 15 years to license and build can be a worse investment than a slightly less revolutionary design that can be replicated on schedule.

BWRX-300 has the strongest evidence that it can become a repeatable product rather than a one-off demonstration. Its first unit is already in construction, and its design intentionally uses substantial existing nuclear technology and infrastructure.

One important caveat

If you're asking because you're considering investing in the companies, rather than choosing a reactor for a utility, my answer changes substantially. The best reactor company and the best stock can be very different bets.

For an investment decision, I'd compare GE Vernova, TerraPower (private), NuScale, Oklo, X-energy (private), and Rolls-Royce on valuation, backlog, dilution/capital needs, probability of commercial deployment, and potential GW of future orders.

No single company can be definitively labeled the absolute best because the "best" choice depends on whether you prioritize immediate regulatory readiness or cutting-edge advanced technology. However, five frontrunners dominate the small modular reactor (SMR) space for clean, reliable baseload power, each excelling in distinct areas:

Top SMR Companies and Their Core Advantages

• NuScale Power : Best for regulatory readiness . It is currently the only developer with an SMR design certified by the U.S. Nuclear Regulatory Commission (NRC). Its light-water VOYGR plants utilize scaled-down, traditional nuclear technology, making them the closest to commercial deployment.
• GE Hitachi Nuclear Energy : Best for grid-scale compatibility . Its BWRX-300 is a 300 MW boiling water reactor heavily favored by major utilities due to its design simplicity and reliance on proven operational mechanisms. It has major deployment backing in Canada, the U.S., and parts of Europe.
• TerraPower : Best for next-generation efficiency and corporate backing . Funded largely by Bill Gates, the company is building its flagship "Natrium" sodium-cooled fast reactor plant in Wyoming. It features an integrated molten salt energy storage system to easily ramp power up and down.
• X-energy : Best for industrial applications . Utilizing high-temperature gas-cooled technology (Xe-100) and proprietary TRISO pebble fuel, its reactors are virtually meltdown-proof. This design excels at producing both high-temperature steam for heavy industry and steady electricity.
• Kairos Power : Best for tech-sector momentum . Utilizing fluoride salt-cooled high-temperature tech, Kairos recently broke ground on its Hermes demonstration reactor. It is notable for signing a major deal to power Google's data centers.

Direct Comparison of Leading SMR Developers

What to Consider When Choosing an SMR Partner

When evaluating these companies for baseload clean energy, you must balance three critical vectors:

1. Fuel Supply Risks : Many advanced SMR designs (like TerraPower and X-energy) require High-Assay Low-Enriched Uranium (HALEU). Traditional light-water SMRs (like NuScale or GE Hitachi) utilize standard low-enriched uranium, bypassing immediate fuel supply chain bottlenecks.
2. Deployment Timelines : While SMRs promise faster factory fabrication, most commercial deployments are slated for the late 2020s or early 2030s.
3. Use Case Requirements : If you strictly need grid electricity, GE Hitachi or NuScale are standard choices. If you run heavy industrial facilities or chemical plants requiring massive process heat alongside power, X-energy or Kairos are superior fits.

Are you looking at these companies from an investment perspective , or are you evaluating SMRs for a specific commercial utility/industrial project ? Let me know so I can provide more relevant timeline or economic data.

If by “best” you mean the strongest combination of technical maturity, licensing progress, construction readiness, and credible path to repeatable clean baseload, my pick today is GE Vernova Hitachi Nuclear Energy (GEH) and its BWRX-300.

My ranking for new clean baseload

Why GEH/BWRX-300 gets my #1:

• It's actually moving into construction. Canada authorized Ontario Power Generation to construct a BWRX-300 at Darlington in April 2025—the first SMR construction license issued in Canada.
• GEH expects the first of four Darlington units to be completed around the end of the decade.
• The underlying reactor technology is evolutionary rather than radically experimental: a simplified boiling-water reactor derived from GE's existing nuclear technology.
• 300 MWe is a useful sweet spot for grid-scale baseload: big enough to matter, but substantially smaller than a conventional gigawatt-class reactor.
• Most importantly, the value proposition isn't merely “we have a reactor design.” The industry needs to prove repeatable construction at predictable cost. That's arguably the central SMR challenge right now. Reuters' latest assessment similarly emphasizes that manufacturing scale, supply chains and repeatable construction—not the physics—are likely to determine the winners.

The interesting wildcard: TerraPower

If you're asking which company could ultimately have the best reactor, rather than which is most bankable for near-term baseload, I'd put TerraPower at #1.

Its Natrium reactor received an NRC construction permit in March 2026—the first NRC construction permit for a commercial non-light-water reactor. www.energy.gov The project is under construction in Wyoming and targets commercial operation around 2031.

Natrium also combines a sodium-cooled fast reactor with molten-salt thermal energy storage. That potentially gives it something conventional SMRs don't have: firm nuclear generation plus the ability to shift output, which could be extremely valuable on grids with lots of wind and solar.

The trade-off is technology risk. BWRX-300 is much more evolutionary; Natrium is much more ambitious.

NuScale is a different case

NuScale deserves credit for being the U.S. licensing leader. The NRC approved its 77-MWe module design in 2025, with a six-module configuration totaling 462 MWe.

But licensing isn't the same thing as building economically. NuScale's previous U.S. project was canceled after projected costs rose substantially. So I'd regard it as a technically credible company with considerably more commercial-execution risk than the headline NRC approval might suggest.

And Rolls-Royce is increasingly compelling

For Europe, I'd put Rolls-Royce SMR much higher. The UK selected it for its first SMR program, and in April 2026 Great British Energy–Nuclear signed the contract to begin delivery of the UK's first SMRs.

Its reactor is roughly 470 MWe, making it less “small” than some competitors but potentially a very attractive unit for conventional grid baseload. It has also accumulated commitments in the UK, Czech Republic and Sweden.

Bottom line

If I were evaluating a utility choosing technology for a new baseload plant today:

🥇 GEH BWRX-300 — best risk-adjusted choice
🥈 TerraPower Natrium — best technological upside
🥉 Rolls-Royce SMR — best European fleet opportunity

One important caveat: I wouldn't assume any SMR is yet proven to beat large conventional nuclear or renewables + storage on pure $/MWh. The economic case depends heavily on financing, construction repetition, grid value and site-specific conditions. A recent 2026 analysis of SMRs for large data centers, for example, found that first-of-a-kind costs can remain substantially above grid power, while nth-of-a-kind manufacturing can radically change the economics.

If you're asking this from an investment perspective—i.e., which publicly traded company/stock has the best risk-reward from the SMR boom—that's a substantially different ranking.

Identifying the "best" small modular reactor (SMR) company depends heavily on whether you prioritize regulatory approval, near-term construction reality , or advanced high-temperature/microreactor capabilities (such as powering remote heavy industry or AI data centers).

The SMR landscape is divided into front-runners with major regulatory and deployment milestones:

• NuScale Power (NYSE: SMR):
  • The Regulatory Leader: NuScale is historic for being the first SMR developer to secure standard design approval and certification from the U.S. Nuclear Regulatory Commission (NRC) for its light-water modular technology.
  • Baseload Outlook: They have advanced multi-gigawatt framework discussions (such as with ENTRA1 Energy and the Tennessee Valley Authority) and international project pipelines, making them the most mature option from a pure regulatory licensing standpoint.
• GE Vernova / GE Hitachi Nuclear Energy (NYSE: GEV):
  • The Utility/Execution Favorite: Their BWRX-300 boiling water SMR leverages decades of proven nuclear engineering. Rather than waiting on unproven concepts, it offers a simplified design aimed at matching the economics of natural gas.
  • Baseload Outlook: GE Hitachi is actively engaged in commercial deployment, most notably leading North America's path to construction with Ontario Power Generation at the Darlington site, alongside selection announcements in Europe like Sweden.
• X-energy:
  • The Industrial & High-Temp Specialist: Backed by major private capital (including Amazon) and the U.S. Department of Energy, X-energy focuses on high-temperature gas reactors (the Xe-100) using proprietary TRISO-X fuel, which eliminates the risk of traditional core melt downs and allows for industrial process heat alongside electricity.
  • Baseload Outlook: They are targeting large-scale fleet deployments across the U.S. and U.K. paired with heavy industrial users like Dow.
• TerraPower:
  • The Advanced Fast Reactor Pioneer: Backed by Bill Gates, TerraPower is building its flagship sodium-cooled fast reactor (Natrium ) in Wyoming on the site of a retiring coal plant, featuring integrated molten salt energy storage to balance the grid.
  • Baseload Outlook: It has achieved major construction permit milestones with the NRC as a non-light-water design and secured robust international construction partnerships.
• Oklo Inc. (NYSE: OKLO):
  • The Microreactor & Data Center Play: Oklo designs compact "Aurora Powerhouses" intended to sit behind-the-meter directly adjacent to major industrial loads or hyperscale data centers, providing 24/7 carbon-free baseload power while bypassing crowded grid interconnection queues.
  • Baseload Outlook: While highly speculative and still pre-revenue awaiting further regulatory milestones, they have massive planned pipelines with tech giants and data center operators.

To help narrow down which company fits your goals, are you looking at this from an investment/stock perspective , or are you evaluating an SMR vendor for a specific commercial, utility, or industrial energy project?

Determining the "best" small modular reactor (SMR) company depends heavily on whether you prioritize regulatory approval, near-term physical construction , or tech-giant backing for data-center baseload power . The SMR landscape is divided between traditional light-water adaptations and next-generation high-temperature/fast reactors.

Leading SMR companies are categorized below by their unique market advantages:

• GE Vernova Hitachi Nuclear Energy (GEV / Hitachi)
  • The Tech: BWRX-300 (300 MW) boiling water small modular reactor.
  • Why they lead: Widely considered the most commercially "bankable" and pragmatic choice. Construction on the BWRX-300 officially commenced at Ontario Power Generation’s Darlington site in mid-2025, pacing it to be the first operational grid-scale SMR in the Western world around 2030. They have robust utility backing globally across North America and Europe.
• X-energy
  • The Tech: Xe-100 high-temperature gas-cooled reactor (80 MW modules) using proprietary TRISO-X spherical fuel.
  • Why they lead: X-energy stands out for heavy industrial and tech integration. They secured major backing from Amazon to deploy multi-reactor campuses for clean data-center power, alongside a high-profile commercial demonstration project with Dow in Texas. Their high outlet temperature also allows for zero-emission industrial process heat.
• NuScale Power (NYSE: SMR)
  • The Tech: NuScale Power Module (scalable 50 MW to 77 MW units configured into multi-module plants).
  • Why they lead: NuScale holds a major regulatory milestone as the first SMR developer to receive standard design approval from the U.S. Nuclear Regulatory Commission (NRC). Backed by strong cash reserves and multi-supplier partnerships (such as with ENTRA1 Energy and regional efforts tied to the Tennessee Valley Authority), they are a pioneer in commercial readiness.
• Oklo Inc. (NYSE: OKLO)
  • The Tech: Aurora powerhouse—a compact, liquid-metal-cooled, fast-fission reactor.
  • Why they lead: Backed heavily by prominent tech figures and specialized for "behind-the-meter" deployment, Oklo has made waves by signing massive multi-gigawatt framework agreements with tech giants like Meta Platforms to power AI data centers directly. Their fast-reactor design can recycle spent nuclear fuel, though they still face the heavy lift of navigating the final NRC commercial licensing phases.
• Westinghouse Electric Company
  • The Tech: AP300 SMR (300 MWe pressurized water reactor derived from the larger, proven AP1000 framework).
  • Why they lead: For risk-averse utilities, Westinghouse offers an evolutionary advantage. Because their larger reactors are already globally licensed and built, the AP300 relies on an existing regulatory and supply chain familiarity that newer startup competitors lack.

Summary Recommendation

• Choose GE Vernova Hitachi if you want the safest bet on actual steel in the ground and a clear path to grid operation before 2030.
• Choose X-energy or Oklo if your goal is localized, dedicated off-grid or behind-the-meter clean baseload power explicitly tailored for heavy industrial or AI data-center scaling.

To help narrow down which company aligns with your goals, let me know:

• Are you looking at this from an investment perspective or for direct energy procurement/offtake?
• Do you prefer light-water traditional designs or advanced generation-IV (gas/liquid metal) reactors?

If the goal is new, clean, firm baseload power—not a speculative reactor concept—my top pick today is GE Vernova Hitachi Nuclear Energy and its BWRX-300.

My ranking for 2026

Why BWRX-300 gets my #1: it is no longer merely a paper design. The first unit is under construction at Ontario Power Generation's Darlington site, with GE Vernova Hitachi targeting commercial operation by the end of 2030. The design also builds heavily on the company's existing boiling-water-reactor technology rather than introducing an entirely new coolant/fuel system.

That matters enormously for baseload. For a utility or large power buyer, I would value execution risk more highly than theoretical efficiency.

The interesting challenger: TerraPower

TerraPower's Natrium is arguably the more exciting technology. It's a 345-MWe sodium-cooled fast reactor paired with thermal energy storage that can boost output to roughly 500 MWe for periods of high demand.

And this isn't hypothetical anymore: the NRC issued Natrium's construction permit in March 2026, and TerraPower formally began construction at Kemmerer, Wyoming, in April.

So I'd frame it:

• Want the highest probability of getting a conventional clean baseload plant deployed? → BWRX-300
• Want the most differentiated next-generation nuclear platform? → Natrium
• Want a potentially attractive investment in advanced nuclear rather than buying power? → That's a different ranking.

One important caveat

I would not put NuScale first despite its impressive regulatory position. The NRC granted its 462-MWe US460 design Standard Design Approval in 2025, but its flagship Utah Carbon Free Power Project was terminated in 2023.

That's a useful lesson: regulatory approval ≠ economically viable deployment.

For clean baseload, I'd therefore weight the companies roughly:

Construction reality > committed customers/sites > supply chain > licensing > economics at scale > reactor elegance.

On that basis, BWRX-300 is currently the safest horse in the Western SMR race, while Natrium has the greater technological upside.

If you're asking because you're considering investing in the companies/stocks, rather than choosing a reactor for a power project, I can rank GE Vernova, TerraPower's private exposure, NuScale, Oklo, Cameco, BWXT, Rolls-Royce and X-energy on risk/reward—that produces a substantially different answer.

Determining the "best" small modular reactor (SMR) company for clean baseload power depends heavily on whether you prioritize regulatory maturity, active construction/deployment , or next-gen tech (like high-temperature heat for industrial use or AI data centers). Because the SMR market is divided between execution-ready designs and visionary startups, the top contenders fall into distinct categories:

• GE Vernova (GE Hitachi Nuclear Energy): Widely considered the most bankable and scalable choice for traditional grid baseload power. Their BWRX-300 SMR leverages proven boiling water reactor tech scaled down into a modular format, and unlike many competitors, they have active construction and deployment pathways underway in North America and Europe.
• NuScale Power: The regulatory pioneer in the U.S. market, NuScale remains unique for holding U.S. Nuclear Regulatory Commission (NRC) approval for its modular designs. They are tailored heavily toward utility-scale deployments and massive multi-gigawatt regional frameworks (such as collaborations with the Tennessee Valley Authority).
• X-energy: A top choice for heavy industry and clean baseload power combined. Their high-temperature gas-cooled reactor (Xe-100) uses specialized TRISO fuel that prevents meltdown, making it exceptionally safe and capable of delivering both electricity and high-temperature heat for industrial manufacturing or chemical plants. They have secured major backing from tech hyperscalers like Amazon and industrial heavyweights like Dow.
• Oklo Inc.: Backed heavily by high-profile investors like Sam Altman, Oklo focuses on fast-fission microreactors (Aurora Powerhouses) that can run on recycled nuclear waste and require refueling only once a decade. They are optimized for behind-the-meter, localized clean baseload power—making them a favorite for localized tech and AI data center campuses.
• TerraPower: Founded by Bill Gates, TerraPower specializes in advanced nuclear architecture (like sodium-cooled fast reactors) and has won critical regulatory approvals to build its commercial demonstration units, positioning it well for long-term scalable clean power.

To help narrow down which company fits your specific goals, let me know:

• Are you looking at this from an investment/stock perspective or for actual energy procurement/project planning?
• Do you need traditional grid-scale power (300 MWe+) or a behind-the-meter microreactor for a localized facility?

If by “best” you mean the company most likely to actually deliver new, clean, 24/7 baseload power at commercial scale, my pick today is GE Vernova / GE Hitachi Nuclear Energy (GEH) and its BWRX-300.

My 2026 ranking

Why GEH is my #1

The decisive factor is “show me the concrete.” GEH isn't merely pitching an SMR anymore.

Ontario Power Generation's Darlington project has a construction licence, and the first BWRX-300 is actually under construction. Canada's nuclear regulator says the first reactor's construction is underway and that the first regulatory hold point was cleared in March 2026.

OPG plans four BWRX-300s at Darlington. Each is roughly 300 MW, making a four-unit site approximately 1.2 GW of dependable generation. GEH says the design targets roughly 24–36 months of construction for subsequent units.

That's extremely important because SMRs only become economically compelling if you can repeat the same design many times. The economic thesis isn't really "small reactors are cheaper." It's:

standardized reactor + factory manufacturing + repeat builds = lower cost and schedule risk.

The BWRX-300 is probably the Western SMR with the strongest opportunity to demonstrate that proposition first.

The most interesting challenger: TerraPower

www.terrapower.com TerraPower's Natrium is arguably the more exciting technology.

It combines an advanced sodium-cooled reactor with thermal energy storage, allowing the plant to produce electricity above the reactor's steady thermal output when needed. That could make nuclear substantially more useful alongside large amounts of intermittent wind and solar.

And this isn't purely theoretical anymore: TerraPower began construction of Kemmerer Unit 1 in Wyoming in April 2026 after receiving its NRC construction permit.

I'd therefore characterize the choice this way:

• Want the lowest technology/deployment risk? → GEH BWRX-300
• Want the most interesting advanced nuclear platform? → TerraPower Natrium
• Want a potentially highly standardized factory-built fleet? → Rolls-Royce SMR
• Want the most regulatory-mature U.S. SMR design? → NuScale

One important caveat: none of these has yet demonstrated a fleet of commercially successful SMRs, so I wouldn't treat advertised $/MWh figures as established facts. SMRs still need to prove that serial production actually produces the hoped-for cost reductions. The nuclear industry's history makes that the central investment question.

If you're asking this from an investment perspective, rather than "which reactor should a utility build?", my ranking changes considerably—I'd look at GE Vernova vs. Oklo vs. NuScale vs. Cameco/uranium/fuel suppliers rather than simply picking the best reactor.