When to Choose Each Option
Clear guidance based on your specific situation and needs.
Our Recommendation
For any new work in mid-2026, Sonnet 5 is the stronger and more current choice: it's the live default (GA June 30, 2026), it tops the coding benchmarks that matter (SWE-bench Pro 63.2%, Terminal-bench 2.1 80.4% — ahead of Opus 4.8), and it wins on browser/agent safety with prompt-injection resistance dropping attacks from 31.5% to 0.93%. GPT-5 only wins on two honest counts: OpenAI's broader multimodal ecosystem, and more predictable token accounting (Sonnet 5's tokenizer inflates counts 1.0–1.35x and its intro $2/$10 pricing jumps to $3/$15 after Aug 31). But the real caveat is currency: GPT-5 has been superseded inside OpenAI by the GPT-5.6 tier line (Sol $5/$30, Terra $2.50/$15, Luna $1/$6). If you're choosing today, pick Sonnet 5 for coding and agents — and if you're locked to OpenAI, evaluate GPT-5.6, not GPT-5. Update (September 29, 2026): Sonnet 5.5 strengthens option A again — it keeps Sonnet 5's $2/$10 pricing (plus $0.20/M cache reads), adds 70.6% on Terminal-Bench 4.0 (Sonnet 5: 10.3%), a 1844 GDPval-AA ELO two points under Opus 5.5, and the family's first cyber safeguards. The gap between a live, improving default and a superseded GPT-5 checkpoint keeps growing.
- Choose Claude Sonnet 5 when...
- You want the current-generation default with the strongest 2026 coding benchmarks (SWE-bench Pro, Terminal-bench, FrontierCode).
- You're cost-sensitive and can lock in the intro $2/$10 pricing before the August 31, 2026 promo cliff.
- You run long-horizon terminal or agentic workflows where Sonnet 5 leads even Opus 4.8.
- Browser or agent workflows where prompt-injection resistance (0.93%) is a hard requirement.
- You want the current Anthropic default that keeps improving — Sonnet 5.5 adds Terminal-Bench 4.0 70.6% and first-of-family cyber safeguards on top of Sonnet 5's 2026 baseline.
- Choose GPT-5 when...
- You're already committed to OpenAI's multimodal ecosystem, tooling and integrations.
- You need predictable, well-understood token accounting without tokenizer inflation.
- You have legacy integrations pinned to GPT-5 that don't yet support the 5.6 line.
- For any genuinely new build, evaluate GPT-5.6 (Sol/Terra/Luna) rather than GPT-5 itself.
- Your stack is contractually or technically bound to the OpenAI API and GPT-5-era integrations you have already validated.