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 67. 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 41. The single biggest benchmark swing on the page is HLE, 44 to 3.
GPT-5.3 Instant is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $1.25 input / $5.00 output per 1M tokens for Gemini 2.5 Pro. That is roughly 2.8x on output cost alone. GPT-5.3 Instant is the reasoning model in the pair, while Gemini 2.5 Pro 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. Gemini 2.5 Pro gives you the larger context window at 1M, compared with 128K for GPT-5.3 Instant.
Pick GPT-5.3 Instant if you want the stronger benchmark profile. Gemini 2.5 Pro only becomes the better choice if you want the cheaper token bill or you need the larger 1M context window.
GPT-5.3 Instant
82.9
Gemini 2.5 Pro
61.7
GPT-5.3 Instant
78.7
Gemini 2.5 Pro
41
GPT-5.3 Instant
95
Gemini 2.5 Pro
85.1
GPT-5.3 Instant
94.2
Gemini 2.5 Pro
80.7
GPT-5.3 Instant
80.8
Gemini 2.5 Pro
58.4
GPT-5.3 Instant
96
Gemini 2.5 Pro
83
GPT-5.3 Instant
93.4
Gemini 2.5 Pro
82.7
GPT-5.3 Instant
97.2
Gemini 2.5 Pro
83.5
GPT-5.3 Instant is ahead overall, 87 to 67. The biggest single separator in this matchup is HLE, where the scores are 44 and 3.
GPT-5.3 Instant has the edge for knowledge tasks in this comparison, averaging 80.8 versus 58.4. 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 41. Inside this category, SWE-bench Pro 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 83.5. 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 80.7. Inside this category, BBH 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 61.7. 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 85.1. 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 83. 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 82.7. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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