Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.3 Codex
89
GPT-5.5
89
Verified leaderboard positions: GPT-5.3 Codex unranked · GPT-5.5 #2
Treat this as a split decision. GPT-5.3 Codex makes more sense if coding is the priority or you want the cheaper token bill; GPT-5.5 is the better fit if agentic is the priority or you need the larger 1M context window.
Agentic
+10.3 difference
Coding
+4.5 difference
GPT-5.3 Codex
GPT-5.5
$1.75 / $14
$5 / $30
79 t/s
N/A
88.26s
N/A
400K
1M
Treat this as a split decision. GPT-5.3 Codex makes more sense if coding is the priority or you want the cheaper token bill; GPT-5.5 is the better fit if agentic is the priority or you need the larger 1M context window.
GPT-5.3 Codex and GPT-5.5 finish on the same provisional overall score, so this is less about a single winner and more about where the edge shows up. The provisional headline says tie; the benchmark table is where the real choice happens.
GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $1.75 input / $14.00 output per 1M tokens for GPT-5.3 Codex. That is roughly 2.1x on output cost alone. GPT-5.5 gives you the larger context window at 1M, compared with 400K for GPT-5.3 Codex.
GPT-5.3 Codex and GPT-5.5 are tied on the provisional overall score, so the right pick depends on which category matters most for your use case.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 63.1 versus 58.6. Inside this category, SWE-bench Pro 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 71.5. Inside this category, OSWorld-Verified is the benchmark that creates the most daylight between them.
For engineers, researchers, and the plain curious — a weekly brief on new models, ranking shifts, and pricing changes.
Free. No spam. Unsubscribe anytime.