Gemini 3.1 Pro vs GPT-5.5

Pick Gemini 3.1 Pro if you want the stronger benchmark profile. GPT-5.5 only becomes the better choice if reasoning is the priority or you want the stronger reasoning-first profile.

Gemini 3.1 Pro finishes one point ahead on BenchLM's provisional leaderboard, 92 to 91. That is enough to call, but not enough to treat as a blowout. This matchup comes down to a few meaningful edges rather than one model dominating the board.

Gemini 3.1 Pro's sharpest advantage is in multimodal & grounded, where it averages 82.8 against 70.4. The single biggest benchmark swing on the page is ARC-AGI-2, 77.1% to 85%. GPT-5.5 does hit back in reasoning, so the answer changes if that is the part of the workload you care about most.

GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $2.00 input / $12.00 output per 1M tokens for Gemini 3.1 Pro. That is roughly 2.5x on output cost alone. GPT-5.5 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.