Claude Sonnet 4.5 vs GPT-5.4 nano

Pick Claude Sonnet 4.5 if you want the stronger benchmark profile. GPT-5.4 nano only becomes the better choice if you want the cheaper token bill or you need the larger 400K context window.

Claude Sonnet 4.5 is clearly ahead on the provisional aggregate, 66 to 60. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Claude Sonnet 4.5's sharpest advantage is in knowledge, where it averages 83.4 against 53.2. The single biggest benchmark swing on the page is OSWorld-Verified, 61.4% to 39%.

Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $0.20 input / $1.25 output per 1M tokens for GPT-5.4 nano. That is roughly 12.0x on output cost alone. GPT-5.4 nano is the reasoning model in the pair, while Claude Sonnet 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. GPT-5.4 nano gives you the larger context window at 400K, compared with 200K for Claude Sonnet 4.5.