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Spec
GPT-5.5
GPT-4o
Intelligence index↑ better
Winner82
72
Speed↑ better
95 tok/s
Winner110 tok/s
Time to first token↓ better
0.42 s
Winner0.4 s
Context window↑ better
Winner400k
128k
Max output↑ better
16k
Winner16k
Input price↓ better
$5.00 / 1M tokens
Winner$2.50 / 1M tokens
Output price↓ better
$15.00 / 1M tokens
Winner$10.00 / 1M tokens
Blended price↓ better
$7.50 / 1M tokens
Winner$4.38 / 1M tokens
License
Proprietary
Proprietary
Input modalities
text, image
text, image, audio
Output modalities
text
text, audio
Benchmark showdown
MMLU
GPT-5.5
90.2
GPT-4o
88.7
MMLU Pro
GPT-5.5
78.0
GPT-4o
73.3
GPQA
GPT-5.5
62.5
GPT-4o
53.1
MATH
GPT-5.5
89.1
GPT-4o
76.6
HumanEval
GPT-5.5
93.0
GPT-4o
90.2
Strengths, weaknesses and best-for
GPT-5.5
Strengths
- Best-in-class reasoning
- Huge 400k context
- Strong tool use and agents
Weaknesses
- Expensive vs Sonnet for non-reasoning tasks
- Higher latency than gpt-5.5-mini
Best for
- Agentic workflows
- Complex coding
- Hard math & research
GPT-4o
Strengths
- Strong multimodal
- Voice-native
- Mature ecosystem
Weaknesses
- Weaker than GPT-5.5 on reasoning
- Smaller context vs newer models
Best for
- General-purpose chat
- Voice apps
- Vision tasks
Quick verdict
- Pick GPT-5.5 if you want it smarter and longer context.
- Pick GPT-4o if you want it faster and cheaper.
Auto-generated from the spec sheet. Always validate on your own evals.
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