Claude Mythos Preview vs Gemini 3.1 Pro

Pick Claude Mythos Preview if you want the stronger benchmark profile. Gemini 3.1 Pro only becomes the better choice if you want the cheaper token bill or you would rather avoid the extra latency and token burn of a reasoning model.

Claude Mythos Preview is clearly ahead on the provisional aggregate, 99 to 94. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Mythos Preview's sharpest advantage is in multimodal & grounded, where it averages 92.7 against 83.9. The single biggest benchmark swing on the page is CharXiv, 93.2% to 80.2%.

Claude Mythos Preview is also the more expensive model on tokens at $25.00 input / $125.00 output per 1M tokens, versus $1.25 input / $5.00 output per 1M tokens for Gemini 3.1 Pro. That is roughly 25.0x on output cost alone. Claude Mythos Preview 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.