Claude Sonnet 4.5 vs o3-mini

Pick Claude Sonnet 4.5 if you want the stronger benchmark profile. o3-mini only becomes the better choice if you want the cheaper token bill or you want the stronger reasoning-first profile.

Claude Sonnet 4.5 is clearly ahead on the provisional aggregate, 66 to 56. 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 coding, where it averages 77.2 against 49.3. The single biggest benchmark swing on the page is SWE-bench Verified, 77.2% to 49.3%.

Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $1.10 input / $4.40 output per 1M tokens for o3-mini. That is roughly 3.4x on output cost alone. o3-mini 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.