GPT-5.1 Codex vs Qwen 3.5 397B
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI wins on 11 of 15 benchmarks against Qwen 3.5 397B by Qwen, which leads on 3. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
General Intelligence: In general intelligence, GPT-5.1 Codex scores 1395 on Chatbot Arena ELO compared to Qwen 3.5 397B's 1350, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to Qwen 3.5 397B's 81.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to Qwen 3.5 397B's 88.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to Qwen 3.5 397B's 76.4%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to Qwen 3.5 397B's 54.0%.
Math: In math, Qwen 3.5 397B scores 87.0% on MATH compared to GPT-5.1 Codex's 85.0%, while both score 95.0% on GSM8K.
Reasoning: In reasoning, GPT-5.1 Codex scores 65.0% on GPQA Diamond compared to Qwen 3.5 397B's 62.0%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to Qwen 3.5 397B's 45.0%.
Context: In context, GPT-5.1 Codex scores 400K on Context Length compared to Qwen 3.5 397B's 262K.
Pricing Comparison
GPT-5.1 Codex costs $1.3/1M input tokens and $10.0/1M output tokens, while Qwen 3.5 397B costs $0.55/1M input and $3.5/1M output. Qwen 3.5 397B is the more affordable option for API usage.
Speed Comparison
GPT-5.1 Codex generates output at 85 tok/s compared to Qwen 3.5 397B's 45 tok/s, and the time to first token is 400 ms for GPT-5.1 Codex versus 600 ms for Qwen 3.5 397B. GPT-5.1 Codex delivers faster throughput.
Verdict
For developers prioritizing coding and general intelligence and speed, GPT-5.1 Codex has the edge. For those who value math and affordability, Qwen 3.5 397B is the stronger choice.
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GPT-5.1 Codex vs Qwen 3.5 397B — FAQ
Which is better, GPT-5.1 Codex or Qwen 3.5 397B?
GPT-5.1 Codex wins on more benchmarks overall (11 vs 3). However, the best choice depends on your specific needs — each model excels in different areas.
How does GPT-5.1 Codex compare to Qwen 3.5 397B for coding?
GPT-5.1 Codex is better for coding, scoring 78.0% on SWE-bench Verified compared to 76.4%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is GPT-5.1 Codex cheaper than Qwen 3.5 397B?
Yes, Qwen 3.5 397B is cheaper. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens. Qwen 3.5 397B costs $0.55/1M input and $3.5/1M output tokens.
Which is faster, GPT-5.1 Codex or Qwen 3.5 397B?
GPT-5.1 Codex is faster, generating output at 85 tok/s compared to 45 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the GPT-5.1 Codex vs Qwen 3.5 397B comparison cover?
This comparison covers 15 benchmarks including Chatbot Arena ELO, MMLU-Pro, HumanEval+, MATH, GPQA Diamond, SWE-bench Verified, Output Speed, LiveCodeBench, and more. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.