Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
o3-mini is clearly ahead on the aggregate, 71 to 66. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
o3-mini's sharpest advantage is in knowledge, where it averages 70.8 against 60.8. The single biggest benchmark swing on the page is MMMU-Pro, 73 to 64. Step 3.5 Flash does hit back in multilingual, so the answer changes if that is the part of the workload you care about most.
o3-mini is also the more expensive model on tokens at $1.10 input / $4.40 output per 1M tokens, versus $0.10 input / $0.30 output per 1M tokens for Step 3.5 Flash. That is roughly 14.7x on output cost alone. o3-mini is the reasoning model in the pair, while Step 3.5 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. Step 3.5 Flash gives you the larger context window at 256K, compared with 200K for o3-mini.
Pick o3-mini if you want the stronger benchmark profile. Step 3.5 Flash only becomes the better choice if multilingual is the priority or you want the cheaper token bill.
o3-mini
66.6
Step 3.5 Flash
60.2
o3-mini
55.6
Step 3.5 Flash
47.1
o3-mini
74.4
Step 3.5 Flash
66.7
o3-mini
81.1
Step 3.5 Flash
78.3
o3-mini
70.8
Step 3.5 Flash
60.8
o3-mini
93.9
Step 3.5 Flash
87
o3-mini
73
Step 3.5 Flash
82.8
o3-mini
87.3
Step 3.5 Flash
84.5
o3-mini is ahead overall, 71 to 66. The biggest single separator in this matchup is MMMU-Pro, where the scores are 73 and 64.
o3-mini has the edge for knowledge tasks in this comparison, averaging 70.8 versus 60.8. Inside this category, GPQA is the benchmark that creates the most daylight between them.
o3-mini has the edge for coding in this comparison, averaging 55.6 versus 47.1. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
o3-mini has the edge for math in this comparison, averaging 87.3 versus 84.5. Inside this category, AIME 2024 is the benchmark that creates the most daylight between them.
o3-mini has the edge for reasoning in this comparison, averaging 81.1 versus 78.3. Inside this category, LongBench v2 is the benchmark that creates the most daylight between them.
o3-mini has the edge for agentic tasks in this comparison, averaging 66.6 versus 60.2. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
o3-mini has the edge for multimodal and grounded tasks in this comparison, averaging 74.4 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
o3-mini has the edge for instruction following in this comparison, averaging 93.9 versus 87. Inside this category, IFEval is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for multilingual tasks in this comparison, averaging 82.8 versus 73. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.
Get notified when new models drop, benchmark scores change, or the leaderboard shifts. One email per week.
Free. No spam. Unsubscribe anytime. We only store derived location metadata for consent routing.