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 52. 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 reasoning, where it averages 78.3 against 49.4. The single biggest benchmark swing on the page is LongBench v2, 74 to 49. GPT-4o mini does hit back in coding, so the answer changes if that is the part of the workload you care about most.
GPT-4o mini is also the more expensive model on tokens at $0.15 input / $0.60 output per 1M tokens, versus $0.10 input / $0.30 output per 1M tokens for Step 3.5 Flash. That is roughly 2.0x on output cost alone. Step 3.5 Flash gives you the larger context window at 256K, compared with 128K for GPT-4o mini.
Pick Step 3.5 Flash if you want the stronger benchmark profile. GPT-4o mini only becomes the better choice if coding is the priority.
Step 3.5 Flash
60.2
GPT-4o mini
50.9
Step 3.5 Flash
47.1
GPT-4o mini
65
Step 3.5 Flash
66.7
GPT-4o mini
60.2
Step 3.5 Flash
78.3
GPT-4o mini
49.4
Step 3.5 Flash
60.8
GPT-4o mini
62
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
GPT-4o mini
74.7
Comparable scores for this category are coming soon. One or both models do not have sourced results here yet.
Step 3.5 Flash is ahead overall, 66 to 52. The biggest single separator in this matchup is LongBench v2, where the scores are 74 and 49.
GPT-4o mini has the edge for knowledge tasks in this comparison, averaging 62 versus 60.8. Inside this category, FrontierScience is the benchmark that creates the most daylight between them.
GPT-4o mini has the edge for coding in this comparison, averaging 65 versus 47.1. Inside this category, SWE-bench Pro 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 49.4. 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 50.9. Inside this category, BrowseComp 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 60.2. 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 74.7. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.
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