Model Comparison

Grok 4.5 vs Nemotron 3 Ultra (550B A55B)Which is better in 2026?

Grok 4.5 shows notably better performance in the majority of benchmarks.

Verdict: Grok 4.5 vs Nemotron 3 Ultra (550B A55B) — which is better?

Grok 4.5 (by xAI) and Nemotron 3 Ultra (550B A55B) (by NVIDIA) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

Grok 4.5 outperforms in 3 benchmarks (GDPval-AA, GPQA, Terminal-Bench 2.1), while Nemotron 3 Ultra (550B A55B) is better at 1 benchmark (OmniScience). Grok 4.5 shows notably better performance in the majority of benchmarks.

Choose Grok 4.5 if…

  • you want the strongest raw capability — it leads on 3 of 4 shared benchmarks
  • you want the most recent training data — it shipped Jul 2026

Choose Nemotron 3 Ultra (550B A55B) if…

  • you need open weights you can self-host or fine-tune

Performance Benchmarks

Comparative analysis across standard metrics

4 benchmarks

Grok 4.5 outperforms in 3 benchmarks (GDPval-AA, GPQA, Terminal-Bench 2.1), while Nemotron 3 Ultra (550B A55B) is better at 1 benchmark (OmniScience).

Grok 4.5 shows notably better performance in the majority of benchmarks.

Mon Jul 27 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Grok 4.5 specifies input context (500,000 tokens).

xAI
Grok 4.5
Input500,000 tokens
Output- tokens
NVIDIA
Nemotron 3 Ultra (550B A55B)
Input- tokens
Output- tokens
Mon Jul 27 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Grok 4.5 supports multimodal inputs, whereas Nemotron 3 Ultra (550B A55B) does not.

Grok 4.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Grok 4.5

Text
Images
Audio
Video

Nemotron 3 Ultra (550B A55B)

Text
Images
Audio
Video

License

Usage and distribution terms

Grok 4.5 is licensed under a proprietary license, while Nemotron 3 Ultra (550B A55B) uses OpenMDW License v1.1.

License differences may affect how you can use these models in commercial or open-source projects.

Grok 4.5

Proprietary

Closed source

Nemotron 3 Ultra (550B A55B)

OpenMDW License v1.1

Open weights

Release Timeline

When each model was launched

Grok 4.5 was released on 2026-07-16, while Nemotron 3 Ultra (550B A55B) was released on 2026-06-04.

Grok 4.5 is 1 month newer than Nemotron 3 Ultra (550B A55B).

Grok 4.5

Jul 16, 2026

1 weeks ago

1mo newer
Nemotron 3 Ultra (550B A55B)

Jun 4, 2026

1 months ago

Knowledge Cutoff

When training data ends

Grok 4.5 has a knowledge cutoff of 2026-02-01, while Nemotron 3 Ultra (550B A55B) has a cutoff of 2025-09-30.

Grok 4.5 has more recent training data (up to 2026-02-01), making it potentially better informed about events through that date compared to Nemotron 3 Ultra (550B A55B) (2025-09-30).

Grok 4.5

Feb 2026

5 mo newer
Nemotron 3 Ultra (550B A55B)

Sep 2025

Outputs Comparison

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Key Takeaways

xAI
Larger context window (500,000 tokens)
Supports multimodal inputs
Higher GDPval-AA score (51.4% vs 39.4%)
Higher GPQA score (93.0% vs 87.0%)
Higher Terminal-Bench 2.1 score (83.3% vs 56.4%)
NVIDIA
Has open weights
Higher OmniScience score (78.7% vs 52.0%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Grok 4.5 and Nemotron 3 Ultra (550B A55B) side-by-side, then vote on the output you prefer.

Grok 4.5
✓ Preferred
Nemotron 3 Ultra (550B A55B)
Open in Playground
AI Model Comparison Table
Feature
xAI
Grok 4.5
NVIDIA
Nemotron 3 Ultra (550B A55B)

FAQ

Common questions about Grok 4.5 vs Nemotron 3 Ultra (550B A55B).

Which is better, Grok 4.5 or Nemotron 3 Ultra (550B A55B)?

Grok 4.5 shows notably better performance in the majority of benchmarks. Grok 4.5 is made by xAI and Nemotron 3 Ultra (550B A55B) is made by NVIDIA. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Grok 4.5 compare to Nemotron 3 Ultra (550B A55B) in benchmarks?

Grok 4.5 scores GPQA: 93.0%, Terminal-Bench 2.1: 83.3%, Artificial Analysis Coding Agent Index v1.1: 76.0%, SWE-Bench Pro: 64.7%, AA-Omniscience Index: 63.0%. Nemotron 3 Ultra (550B A55B) scores RULER: 94.7%, IMO-AnswerBench: 92.3%, PinchBench: 90.0%, LiveCodeBench v6: 89.0%, GPQA: 87.0%.

What are the context window sizes for Grok 4.5 and Nemotron 3 Ultra (550B A55B)?

Grok 4.5 supports 500K tokens and Nemotron 3 Ultra (550B A55B) supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Grok 4.5 and Nemotron 3 Ultra (550B A55B)?

Key differences include multimodal support (yes vs no), licensing (Proprietary vs OpenMDW License v1.1). See the full comparison above for benchmark-by-benchmark results.

Who makes Grok 4.5 and Nemotron 3 Ultra (550B A55B)?

Grok 4.5 is developed by xAI and Nemotron 3 Ultra (550B A55B) is developed by NVIDIA.

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