Opus 5 vs Sonnet 5

The comparison most teams actually need to make

This is the pairing most workloads genuinely weigh against each other, since both sit in the practical range for real production work rather than at either extreme of the lineup. Opus 5 costs more per token and carries thinking on by default; Sonnet 5 is meaningfully cheaper and was specifically built to close the quality gap with Opus on coding and agentic tasks rather than trail far behind it the way an entry-level model would.

Where the price gap is worth paying, and where it isn't

For tasks near the genuine ceiling of difficulty — ambiguous, high-stakes, multi-step work — the price gap tends to be worth paying, since a wrong or shallow answer costs more than the extra tokens. For routine, well-scoped work, Sonnet 5's narrower gap to Opus quality on exactly this kind of task, at a substantially lower price, usually makes it the better default rather than a compromise.

Testing both against the same task before committing

Because the two are close enough in capability on a meaningful slice of real work, the most reliable way to choose is running your actual hardest and most typical tasks against both and comparing output quality directly, rather than deciding from the price gap alone.

Related

See the model picker for a recommendation tailored to your specific task shape and budget rather than a general comparison, and Sonnet 5 vs Haiku 4.5 for the next comparison down the cost curve.