Claude Opus 4.6 vs Gemini 3.5 Flash

Pick Gemini 3.5 Flash if you want the stronger benchmark profile. Claude Opus 4.6 only becomes the better choice if knowledge is the priority or you would rather avoid the extra latency and token burn of a reasoning model.

Gemini 3.5 Flash finishes one point ahead on BenchLM's provisional leaderboard, 88 to 87. 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 3.5 Flash's sharpest advantage is in multimodal & grounded, where it averages 83.8 against 77.3. The single biggest benchmark swing on the page is HLE, 53% to 40.2%. Claude Opus 4.6 does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.

Claude Opus 4.6 is also the more expensive model on tokens at $5.00 input / $25.00 output per 1M tokens, versus $1.50 input / $9.00 output per 1M tokens for Gemini 3.5 Flash. That is roughly 2.8x on output cost alone. Gemini 3.5 Flash is the reasoning model in the pair, while Claude Opus 4.6 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.