DeepSeek V4 Pro vs GPT-5.5 Pro

Pick GPT-5.5 Pro if you want the stronger benchmark profile. DeepSeek V4 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.

GPT-5.5 Pro is clearly ahead on the provisional aggregate, 100 to 71. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.5 Pro's sharpest advantage is in agentic, where it averages 90.1 against 59.1. The single biggest benchmark swing on the page is HLE, 7.7% to 57.2%.

GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $1.74 input / $3.48 output per 1M tokens for DeepSeek V4 Pro. That is roughly 51.7x on output cost alone. GPT-5.5 Pro is the reasoning model in the pair, while DeepSeek V4 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.