Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
GPT-5 mini has the cleaner overall profile here, landing at 69 versus 66. It is a real lead, but still close enough that category-level strengths matter more than the headline number.
GPT-5 mini's sharpest advantage is in multimodal & grounded, where it averages 83.8 against 66.7. The single biggest benchmark swing on the page is MMMU-Pro, 86 to 64. Step 3.5 Flash does hit back in instruction following, so the answer changes if that is the part of the workload you care about most.
GPT-5 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 128K for GPT-5 mini.
Pick GPT-5 mini if you want the stronger benchmark profile. Step 3.5 Flash only becomes the better choice if instruction following is the priority or you need the larger 256K context window.
GPT-5 mini
65.7
Step 3.5 Flash
60.2
GPT-5 mini
42.8
Step 3.5 Flash
47.1
GPT-5 mini
83.8
Step 3.5 Flash
66.7
GPT-5 mini
81.8
Step 3.5 Flash
78.3
GPT-5 mini
62.8
Step 3.5 Flash
60.8
GPT-5 mini
82
Step 3.5 Flash
87
GPT-5 mini
80.1
Step 3.5 Flash
82.8
GPT-5 mini
87.2
Step 3.5 Flash
84.5
GPT-5 mini is ahead overall, 69 to 66. The biggest single separator in this matchup is MMMU-Pro, where the scores are 86 and 64.
GPT-5 mini has the edge for knowledge tasks in this comparison, averaging 62.8 versus 60.8. Inside this category, MMLU 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 42.8. Inside this category, LiveCodeBench is the benchmark that creates the most daylight between them.
GPT-5 mini has the edge for math in this comparison, averaging 87.2 versus 84.5. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.
GPT-5 mini has the edge for reasoning in this comparison, averaging 81.8 versus 78.3. Inside this category, LongBench v2 is the benchmark that creates the most daylight between them.
GPT-5 mini has the edge for agentic tasks in this comparison, averaging 65.7 versus 60.2. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
GPT-5 mini has the edge for multimodal and grounded tasks in this comparison, averaging 83.8 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for instruction following in this comparison, averaging 87 versus 82. 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 80.1. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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