Claude Opus vs Sonnet vs Haiku: Which Should You Use?

The article recommends Claude Sonnet 5.5 as the default, Haiku 5.5 for high-volume and sub-agent work, and Opus 5.5 for long, ambiguous tasks where errors are costly. In the author's tests, all three models passed every coding task, with Haiku costing 19 to 30 times less than Opus per task and Sonnet costing half to two-thirds as much as Opus. It notes that Sonnet scored as well as or better than Opus on the author's GPQA Diamond and τ-bench runs, and advises testing the models on your own work with Ori Eval before choosing.