Gemini 2.5 Pro Reasoning vs Grok 3 Pro: which model should you choose?
We compared Gemini 2.5 Pro Reasoning and Grok 3 Pro on price, context window and 12 benchmarks. Gemini 2.5 Pro Reasoning and Grok 3 Pro are effectively tied on the index average; Gemini 2.5 Pro Reasoning is cheaper on a blended 3:1 basis.
Gemini 2.5 Pro Reasoning
Gemini 2.5 Pro Reasoning is a frontier model from Google DeepMind. It offers a 128,000-token context window, costs $16.81 per million input tokens and $67.95 per million output tokens, and averages 83.8 across the index's benchmark suite.
- Input
- $16.81 / 1M
- Output
- $67.95 / 1M
- Context
- 128,000
- Avg score
- 83.8
- Open weights
- No
Grok 3 Pro
Grok 3 Pro is a frontier model from xAI. It offers a 400,000-token context window, costs $16.61 per million input tokens and $73.49 per million output tokens, and averages 83.8 across the index's benchmark suite.
- Input
- $16.61 / 1M
- Output
- $73.49 / 1M
- Context
- 400,000
- Avg score
- 83.8
- Open weights
- No
Specification comparison
| Spec | Gemini 2.5 Pro Reasoning | Grok 3 Pro | Edge |
|---|---|---|---|
| Input price / 1M | $16.81 | $16.61 | B |
| Output price / 1M | $67.95 | $73.49 | A |
| Context window | 128,000 | 400,000 | B |
| Max output | 4,096 | 4,096 | Tie |
| Average score | 83.8 | 83.8 | Tie |
| Arena Elo | 1472.1 | 1448.4 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Gemini 2.5 Pro Reasoning wins 6, Grok 3 Pro wins 6, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Gemini 2.5 Pro Reasoning | Grok 3 Pro | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 86.8 | 83.5 | 3.3 | Gemini 2.5 Pro Reasoning |
| GPQA Diamond | 80.0 | 81.3 | 1.3 | Grok 3 Pro |
| SWE-bench Verified | 71.2 | 71.4 | 0.2 | Grok 3 Pro |
| HumanEval | 86.7 | 89.9 | 3.2 | Grok 3 Pro |
| MATH-500 | 87.9 | 87.0 | 0.9 | Gemini 2.5 Pro Reasoning |
| AIME 2025 | 84.2 | 85.5 | 1.3 | Grok 3 Pro |
| LiveCodeBench | 74.8 | 80.7 | 5.9 | Grok 3 Pro |
| IFEval | 90.8 | 88.6 | 2.2 | Gemini 2.5 Pro Reasoning |
| TruthfulQA | 84.0 | 84.6 | 0.6 | Grok 3 Pro |
| HellaSwag | 92.1 | 90.7 | 1.4 | Gemini 2.5 Pro Reasoning |
| MMMU | 82.8 | 78.9 | 3.9 | Gemini 2.5 Pro Reasoning |
| Arena Elo | 1472.1 | 1448.4 | 23.7 | Gemini 2.5 Pro Reasoning |
Price analysis
On a blended 3:1 input-to-output basis, Gemini 2.5 Pro Reasoning costs about $29.59 per million tokens and Grok 3 Pro costs about $30.83. Gemini 2.5 Pro Reasoning is roughly 4% cheaper than Grok 3 Pro. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Grok 3 Pro has the larger context window at 400,000 tokens, compared with 128,000 for Gemini 2.5 Pro Reasoning. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Gemini 2.5 Pro Reasoning wins 6, Grok 3 Pro wins 6, and 0 are tied. The two models are effectively tied on the index average at 83.8.
The price picture favours Gemini 2.5 Pro Reasoning. The context picture favours Grok 3 Pro. Those two dimensions often matter more than a few benchmark points once a model is good enough for the task.
If you need a single default, start with Gemini 2.5 Pro Reasoning if cost is the constraint and Grok 3 Pro if context is the constraint. Test both on a sample of your own traffic before committing.
Choose Gemini 2.5 Pro Reasoning if
- Unit cost matters and you want the cheaper blended price.
Choose Grok 3 Pro if
- You need the larger 400,000-token context window.
FAQ
Is Gemini 2.5 Pro Reasoning better than Grok 3 Pro?
The two models are effectively tied on the index average at 83.8. The better choice depends on price, context and your task. Gemini 2.5 Pro Reasoning wins 6 benchmarks, Grok 3 Pro wins 6.
Which is cheaper, Gemini 2.5 Pro Reasoning or Grok 3 Pro?
Gemini 2.5 Pro Reasoning is cheaper on a blended 3:1 basis at about $29.59 per million tokens, versus $30.83 for Grok 3 Pro.
Which has the larger context window?
Grok 3 Pro has the larger context window at 400,000 tokens. Gemini 2.5 Pro Reasoning has 128,000 tokens.
Are these models open weights?
Gemini 2.5 Pro Reasoning is proprietary; Grok 3 Pro is proprietary.
Which should I choose for production?
If you need a single default, start with Gemini 2.5 Pro Reasoning if cost is the constraint and Grok 3 Pro if context is the constraint. Test both on a sample of your own traffic before committing.