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 62. 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 40.4. The single biggest benchmark swing on the page is LiveCodeBench, 75 to 36.
GPT-5.3 Instant is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $0.50 input / $3.00 output per 1M tokens for Gemini 3 Flash. That is roughly 4.7x on output cost alone. GPT-5.3 Instant is the reasoning model in the pair, while Gemini 3 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. Gemini 3 Flash 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 3 Flash 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 3 Flash
57.5
GPT-5.3 Instant
78.7
Gemini 3 Flash
40.4
GPT-5.3 Instant
95
Gemini 3 Flash
79.6
GPT-5.3 Instant
94.2
Gemini 3 Flash
72
GPT-5.3 Instant
80.8
Gemini 3 Flash
52.9
GPT-5.3 Instant
96
Gemini 3 Flash
85
GPT-5.3 Instant
93.4
Gemini 3 Flash
80.5
GPT-5.3 Instant
97.2
Gemini 3 Flash
74
GPT-5.3 Instant is ahead overall, 87 to 62. The biggest single separator in this matchup is LiveCodeBench, where the scores are 75 and 36.
GPT-5.3 Instant has the edge for knowledge tasks in this comparison, averaging 80.8 versus 52.9. 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 40.4. Inside this category, LiveCodeBench 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 74. 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 72. 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 57.5. 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 79.6. 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 85. 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 80.5. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.
Get notified when new models drop, benchmark scores change, or the leaderboard shifts. One email per week.
Free. No spam. Unsubscribe anytime. We only store derived location metadata for consent routing.