Gemini 3 Flash Reasoning vs Grok 3 Pro: which model should you choose?
We compared Gemini 3 Flash Reasoning and Grok 3 Pro on price, context window and 12 benchmarks. Grok 3 Pro has the stronger average benchmark score; Gemini 3 Flash Reasoning is cheaper on a blended 3:1 basis.
Gemini 3 Flash Reasoning
Gemini 3 Flash Reasoning is a frontier model from Google DeepMind. It offers a 128,000-token context window, costs $17.05 per million input tokens and $66.77 per million output tokens, and averages 83.7 across the index's benchmark suite.
- Input
- $17.05 / 1M
- Output
- $66.77 / 1M
- Context
- 128,000
- Avg score
- 83.7
- 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 3 Flash Reasoning | Grok 3 Pro | Edge |
|---|---|---|---|
| Input price / 1M | $17.05 | $16.61 | B |
| Output price / 1M | $66.77 | $73.49 | A |
| Context window | 128,000 | 400,000 | B |
| Max output | 32,768 | 4,096 | A |
| Average score | 83.7 | 83.8 | B |
| Arena Elo | 1446.9 | 1448.4 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Gemini 3 Flash Reasoning wins 7, Grok 3 Pro wins 5, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Gemini 3 Flash Reasoning | Grok 3 Pro | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.2 | 83.5 | 3.7 | Gemini 3 Flash Reasoning |
| GPQA Diamond | 81.8 | 81.3 | 0.5 | Gemini 3 Flash Reasoning |
| SWE-bench Verified | 72.5 | 71.4 | 1.1 | Gemini 3 Flash Reasoning |
| HumanEval | 86.9 | 89.9 | 3.0 | Grok 3 Pro |
| MATH-500 | 86.2 | 87.0 | 0.8 | Grok 3 Pro |
| AIME 2025 | 79.4 | 85.5 | 6.1 | Grok 3 Pro |
| LiveCodeBench | 77.7 | 80.7 | 3.0 | Grok 3 Pro |
| IFEval | 90.2 | 88.6 | 1.6 | Gemini 3 Flash Reasoning |
| TruthfulQA | 86.6 | 84.6 | 2.0 | Gemini 3 Flash Reasoning |
| HellaSwag | 92.2 | 90.7 | 1.5 | Gemini 3 Flash Reasoning |
| MMMU | 79.8 | 78.9 | 0.9 | Gemini 3 Flash Reasoning |
| Arena Elo | 1446.9 | 1448.4 | 1.5 | Grok 3 Pro |
Price analysis
On a blended 3:1 input-to-output basis, Gemini 3 Flash Reasoning costs about $29.48 per million tokens and Grok 3 Pro costs about $30.83. Gemini 3 Flash 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 3 Flash Reasoning. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Gemini 3 Flash Reasoning wins 7, Grok 3 Pro wins 5, and 0 are tied. On the index average, Grok 3 Pro leads Gemini 3 Flash Reasoning by 0.1 points (83.8 versus 83.7).
The price picture favours Gemini 3 Flash 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 Grok 3 Pro for quality-sensitive work and Gemini 3 Flash Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Gemini 3 Flash Reasoning if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 32,768-token output limit.
Choose Grok 3 Pro if
- You want the higher average benchmark score in this index.
- You need the larger 400,000-token context window.
FAQ
Is Gemini 3 Flash Reasoning better than Grok 3 Pro?
On the index average, Grok 3 Pro leads Gemini 3 Flash Reasoning by 0.1 points (83.8 versus 83.7). The better choice depends on price, context and your task. Gemini 3 Flash Reasoning wins 7 benchmarks, Grok 3 Pro wins 5.
Which is cheaper, Gemini 3 Flash Reasoning or Grok 3 Pro?
Gemini 3 Flash Reasoning is cheaper on a blended 3:1 basis at about $29.48 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 3 Flash Reasoning has 128,000 tokens.
Are these models open weights?
Gemini 3 Flash Reasoning is proprietary; Grok 3 Pro is proprietary.
Which should I choose for production?
If you need a single default, start with Grok 3 Pro for quality-sensitive work and Gemini 3 Flash Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.