DeepSeek V4 Flash vs GPT-5.4 Pro

Pick GPT-5.4 Pro if you want the stronger benchmark profile. DeepSeek V4 Flash 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.

GPT-5.4 Pro is clearly ahead on the provisional aggregate, 91 to 59. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.4 Pro's sharpest advantage is in agentic, where it averages 89.3 against 49.1. The single biggest benchmark swing on the page is HLE, 8.1% to 58.7%.

GPT-5.4 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $0.14 input / $0.28 output per 1M tokens for DeepSeek V4 Flash. That is roughly 642.9x on output cost alone. GPT-5.4 Pro is the reasoning model in the pair, while DeepSeek V4 Flash 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. GPT-5.4 Pro gives you the larger context window at 1.05M, compared with 1M for DeepSeek V4 Flash.