Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
GPT-5.3 Instant is clearly ahead on the aggregate, 87 to 56. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.3 Instant's sharpest advantage is in coding, where it averages 78.7 against 27.6. The single biggest benchmark swing on the page is SWE-bench Verified, 76 to 24.
GPT-5.3 Instant is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $0.08 input / $0.30 output per 1M tokens for Seed 1.6 Flash. That is roughly 46.7x on output cost alone. Seed 1.6 Flash gives you the larger context window at 256K, compared with 128K for GPT-5.3 Instant.
Pick GPT-5.3 Instant if you want the stronger benchmark profile. Seed 1.6 Flash only becomes the better choice if you want the cheaper token bill or you need the larger 256K context window.
GPT-5.3 Instant
82.9
Seed 1.6 Flash
54.5
GPT-5.3 Instant
78.7
Seed 1.6 Flash
27.6
GPT-5.3 Instant
95
Seed 1.6 Flash
73.1
GPT-5.3 Instant
94.2
Seed 1.6 Flash
66.8
GPT-5.3 Instant
80.8
Seed 1.6 Flash
47.3
GPT-5.3 Instant
96
Seed 1.6 Flash
81
GPT-5.3 Instant
93.4
Seed 1.6 Flash
72.8
GPT-5.3 Instant
97.2
Seed 1.6 Flash
67.1
GPT-5.3 Instant is ahead overall, 87 to 56. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 76 and 24.
GPT-5.3 Instant has the edge for knowledge tasks in this comparison, averaging 80.8 versus 47.3. Inside this category, HLE is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for coding in this comparison, averaging 78.7 versus 27.6. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for math in this comparison, averaging 97.2 versus 67.1. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for reasoning in this comparison, averaging 94.2 versus 66.8. Inside this category, SimpleQA is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for agentic tasks in this comparison, averaging 82.9 versus 54.5. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for multimodal and grounded tasks in this comparison, averaging 95 versus 73.1. Inside this category, OfficeQA Pro is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for instruction following in this comparison, averaging 96 versus 81. Inside this category, IFEval is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for multilingual tasks in this comparison, averaging 93.4 versus 72.8. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.
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