OpenAIGPT-5.5VSZ.ai (Zhipu AI)GLM-5.1
Our Take
We recommend GPT-5.5 if your workflow requires peak reasoning performance, or the 5.2x cheaper GLM-5.1 to optimize your API budget. While both models deliver similar coding capabilities, GPT-5.5 holds a clear lead in reasoning. Choose GPT-5.5 for complex logic, or GLM-5.1 for cost optimization.
▶WHY?
Benchmark Calculations & Evidence:
Coding Benchmarks: Both models were evaluated on the SWE-bench Pro benchmark. GPT-5.5 scored 58.6%, while GLM-5.1 scored 58.4%.
Reasoning Benchmarks: Both models were evaluated on the GPQA Diamond benchmark. GPT-5.5 scored 93.6%, while GLM-5.1 scored 86.2%.
Cost Efficiency: GLM-5.1 pricing ($1.4/M input, $4.4/M output) is 5.2x cheaper than GPT-5.5 ($5/M input, $30/M output).
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Benchmarks & Scores
Coding (swe-bench-pro)Winner (+0.2%)
58.6%complex codebases, multi-file repositories, and architectural planning
Reasoning (gpqa-diamond)Winner (+7.4%)
93.6%graduate-level science QA
Cost & Context
Cost (per 1M tokens)
$11.25Input: $5.00 | Output: $30.00Context WindowLarger
1.05M tokensBenchmarks & Scores
Coding (swe-bench-pro)
58.4%complex codebases, multi-file repositories, and architectural planning
Reasoning (gpqa-diamond)
86.2%graduate-level science QA
Cost & Context
Cost (per 1M tokens)5.2x cheaper
$2.15Input: $1.40 | Output: $4.40Context Window
202.75k tokensFrequently Asked Questions about GPT-5.5 vs GLM-5.1
GLM-5.1 is cheaper than GPT-5.5. GLM-5.1 has a blended cost of $2.15/1M tokens, which is about 5.2x cheaper than GPT-5.5 at $11.25/1M tokens.
GPT-5.5 is better for coding tasks on this benchmark. It scores 58.6% on swe-bench-pro (complex codebases, multi-file repositories, and architectural planning) compared to GLM-5.1 which scores 58.4%.
Related Matchups
Explore similar comparisons for GPT-5.5 and GLM-5.1.
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