Claude Opus 4.5 vs DeepSeek V4 Flash (Max)

Pick Claude Opus 4.5 if you want the stronger benchmark profile. DeepSeek V4 Flash (Max) only becomes the better choice if coding is the priority or you want the cheaper token bill.

Claude Opus 4.5 finishes one point ahead on BenchLM's provisional leaderboard, 78 to 77. 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.

Claude Opus 4.5's sharpest advantage is in knowledge, where it averages 66.2 against 60. The single biggest benchmark swing on the page is SWE-bench Pro, 57.1% to 52.6%. DeepSeek V4 Flash (Max) does hit back in coding, so the answer changes if that is the part of the workload you care about most.

Claude Opus 4.5 is also the more expensive model on tokens at $5.00 input / $25.00 output per 1M tokens, versus $0.14 input / $0.28 output per 1M tokens for DeepSeek V4 Flash (Max). That is roughly 89.3x on output cost alone. DeepSeek V4 Flash (Max) is the reasoning model in the pair, while Claude Opus 4.5 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. DeepSeek V4 Flash (Max) gives you the larger context window at 1M, compared with 200K for Claude Opus 4.5.