Kimi K2.5 vs Mistral Medium 3.5 128B

Pick Mistral Medium 3.5 128B if you want the stronger benchmark profile. Kimi K2.5 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.

Mistral Medium 3.5 128B is clearly ahead on the provisional aggregate, 78 to 63. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Mistral Medium 3.5 128B's sharpest advantage is in coding, where it averages 77.6 against 64.2. The single biggest benchmark swing on the page is SWE-bench Verified, 76.8% to 77.6%.

Mistral Medium 3.5 128B is also the more expensive model on tokens at $1.50 input / $7.50 output per 1M tokens, versus $0.60 input / $3.00 output per 1M tokens for Kimi K2.5. That is roughly 2.5x on output cost alone. Mistral Medium 3.5 128B is the reasoning model in the pair, while Kimi K2.5 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.