Side-by-side comparison of pricing, 12 benchmarks, and generation speed.
| Metric | GPT-5 Codex (high) | Claude Sonnet 5 (Adaptive Reasoning, Low Effort) |
|---|---|---|
| Input ($/M tokens) | $1.25 | $2 |
| Output ($/M tokens) | $10 | $10 |
Verdict. GPT-5 Codex (high) wins the overall benchmark matchup 1–0 across 1 overlapping categories, but raw benchmark score is only one input to the decision.
Pricing. Both models sit in the mid-tier bracket for output-token pricing. At 1.0× the per-million-token cost, Claude Sonnet 5 (Adaptive Reasoning, Low Effort) is meaningfully cheaper if your traffic is output-heavy (long completions, document generation, agent loops). Claude Sonnet 5 (Adaptive Reasoning, Low Effort) makes more sense when output volume is low and absolute reasoning quality justifies the premium.
Strengths. GPT-5 Codex (high) is strongest on Intelligence Index (24.9). Claude Sonnet 5 (Adaptive Reasoning, Low Effort) leads on Intelligence Index (24.7).
Speed. Speed data is incomplete for this pair; benchmark and price should decide.
Provider. OpenAI and Anthropic sell to overlapping but distinct developer audiences: OpenAI tends to ship frontier reasoning models with premium positioning, while Anthropic often prices more aggressively. Your existing vendor relationships, billing, and SLA preferences may matter as much as the raw numbers above.
Workload cost. Workload scenarios (per million requests at 30M input + 15M output tokens): GPT-5 Codex (high) costs $187.50 ($2250/year); Claude Sonnet 5 (Adaptive Reasoning, Low Effort) costs $210.00 ($2520/year). At a smaller 5M-input/2M-output scale (single-developer tool or prototype): GPT-5 Codex (high) ≈ $26.25/run, Claude Sonnet 5 (Adaptive Reasoning, Low Effort) ≈ $30.00/run. At agent/realtime scale (200M input / 100M output per million requests): GPT-5 Codex (high) ≈ $1250/run, Claude Sonnet 5 (Adaptive Reasoning, Low Effort) ≈ $1400/run. GPT-5 Codex (high) becomes more attractive at higher volume — the absolute per-token pricing difference compounds when you ship at scale.
Recommendation. Both models have legitimate use cases — the right answer depends on whether you are optimizing for benchmark ceiling, latency, or unit cost. Start with the cheaper / faster model, evaluate against your specific task, and only switch if the upgrade shows a meaningful lift.
Head-to-head deltas
Data from Artificial Analysis API — 12 benchmarks
GPT-5 Codex (high) is cheaper overall. Its blended price (3:1 input/output ratio) is $3.44/M tokens vs $4.00/M for Claude Sonnet 5 (Adaptive Reasoning, Low Effort).
GPT-5 Codex (high) wins 1 out of 12 benchmarks compared to 0 for Claude Sonnet 5 (Adaptive Reasoning, Low Effort). See the detailed benchmark chart above for per-category results.
Claude Sonnet 5 (Adaptive Reasoning, Low Effort) generates tokens faster at 57 tok/s vs — tok/s. However, Claude Sonnet 5 (Adaptive Reasoning, Low Effort) has lower time-to-first-token (0.98s vs —s).
Choose based on your priorities: GPT-5 Codex (high) for lower cost, GPT-5 Codex (high) for stronger benchmark performance, and Claude Sonnet 5 (Adaptive Reasoning, Low Effort) for faster generation. For latency-sensitive apps, check the TTFT comparison above.