Gemini 3.1 Pro vs Gemma 4 31B

Pick Gemini 3.1 Pro if you want the stronger benchmark profile. Gemma 4 31B only becomes the better choice if you want the cheaper token bill or you want the stronger reasoning-first profile.

Gemini 3.1 Pro is clearly ahead on the provisional aggregate, 92 to 65. 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 multimodal & grounded, where it averages 82.8 against 76.9. The single biggest benchmark swing on the page is MMMU-Pro, 83.9% to 76.9%.

Gemini 3.1 Pro is also the more expensive model on tokens at $2.00 input / $12.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for Gemma 4 31B. That is roughly Infinityx on output cost alone. Gemma 4 31B 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. Gemini 3.1 Pro gives you the larger context window at 1M, compared with 256K for Gemma 4 31B.