Claude 3.5 Sonnet vs GPT-5.5

Pick GPT-5.5 if you want the stronger benchmark profile. Claude 3.5 Sonnet 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 is clearly ahead on the provisional aggregate, 89 to 42. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.5's sharpest advantage is in coding, where it averages 58.6 against 49. The single biggest benchmark swing on the page is GPQA, 59.4% to 93.6%.

GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $3.00 input / $15.00 output per 1M tokens for Claude 3.5 Sonnet. That is roughly 2.0x on output cost alone. GPT-5.5 is the reasoning model in the pair, while Claude 3.5 Sonnet 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-5.5 gives you the larger context window at 1M, compared with 200K for Claude 3.5 Sonnet.