Gemini 3.1 Pro vs Grok 4.20

Pick Gemini 3.1 Pro if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if you want the cheaper token bill or you need the larger 2M context window.

Gemini 3.1 Pro is clearly ahead on the provisional aggregate, 92 to 73. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Gemini 3.1 Pro's sharpest advantage is in reasoning, where it averages 77.1 against 53.3. The single biggest benchmark swing on the page is ARC-AGI-2, 77.1% to 53.3%.

Gemini 3.1 Pro is also the more expensive model on tokens at $2.00 input / $12.00 output per 1M tokens, versus $2.00 input / $6.00 output per 1M tokens for Grok 4.20. That is roughly 2.0x on output cost alone. Grok 4.20 is the reasoning model in the pair, while Gemini 3.1 Pro is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. Grok 4.20 gives you the larger context window at 2M, compared with 1M for Gemini 3.1 Pro.