Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
Step 3.5 Flash is clearly ahead on the aggregate, 66 to 45. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Step 3.5 Flash's sharpest advantage is in multilingual, where it averages 82.8 against 52. The single biggest benchmark swing on the page is MMLU-ProX, 81 to 52. o1-pro does hit back in knowledge, so the answer changes if that is the part of the workload you care about most.
o1-pro is also the more expensive model on tokens at $150.00 input / $600.00 output per 1M tokens, versus $0.10 input / $0.30 output per 1M tokens for Step 3.5 Flash. That is roughly 2000.0x on output cost alone. o1-pro 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 o1-pro.
Pick Step 3.5 Flash if you want the stronger benchmark profile. o1-pro only becomes the better choice if knowledge is the priority or you want the stronger reasoning-first profile.
Step 3.5 Flash
60.2
o1-pro
39.7
Step 3.5 Flash
47.1
o1-pro
23
Step 3.5 Flash
66.7
o1-pro
48.5
Step 3.5 Flash
78.3
o1-pro
56.2
Step 3.5 Flash
60.8
o1-pro
69.9
Comparable scores for this category are coming soon. One or both models do not have sourced results here yet.
Step 3.5 Flash
82.8
o1-pro
52
Step 3.5 Flash
84.5
o1-pro
86
Step 3.5 Flash is ahead overall, 66 to 45. The biggest single separator in this matchup is MMLU-ProX, where the scores are 81 and 52.
o1-pro has the edge for knowledge tasks in this comparison, averaging 69.9 versus 60.8. Inside this category, FrontierScience is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for coding in this comparison, averaging 47.1 versus 23. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
o1-pro has the edge for math in this comparison, averaging 86 versus 84.5. Inside this category, AIME 2024 is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for reasoning in this comparison, averaging 78.3 versus 56.2. Inside this category, LongBench v2 is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for agentic tasks in this comparison, averaging 60.2 versus 39.7. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 66.7 versus 48.5. Inside this category, OfficeQA Pro 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 52. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.
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