Head-to-head comparison across 3benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
DeepSeek V4 Flash
59
GPT-5.5
93
Verified leaderboard positions: DeepSeek V4 Flash #23 · GPT-5.5 #3
Pick GPT-5.5 if you want the stronger benchmark profile. DeepSeek V4 Flash only becomes the better choice if you want the cheaper token bill or you would rather avoid the extra latency and token burn of a reasoning model.
Agentic
+32.7 difference
Coding
+1.5 difference
Knowledge
+21.2 difference
DeepSeek V4 Flash
GPT-5.5
$0.14 / $0.28
$5 / $30
N/A
N/A
N/A
N/A
1M
1M
Pick GPT-5.5 if you want the stronger benchmark profile. DeepSeek V4 Flash only becomes the better choice if you want the cheaper token bill or you would rather avoid the extra latency and token burn of a reasoning model.
GPT-5.5 is clearly ahead on the provisional aggregate, 93 to 59. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5's sharpest advantage is in agentic, where it averages 81.8 against 49.1. The single biggest benchmark swing on the page is HLE, 8.1% to 52.2%.
GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $0.14 input / $0.28 output per 1M tokens for DeepSeek V4 Flash. That is roughly 107.1x on output cost alone. GPT-5.5 is the reasoning model in the pair, while DeepSeek V4 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.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 93 to 59. The biggest single separator in this matchup is HLE, where the scores are 8.1% and 52.2%.
GPT-5.5 has the edge for knowledge tasks in this comparison, averaging 66.4 versus 45.2. Inside this category, HLE is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for coding in this comparison, averaging 58.6 versus 57.1. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for agentic tasks in this comparison, averaging 81.8 versus 49.1. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
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