The reasoning xhigh one is pretty solid: https://simonwillison.net/2026/Apr/23/gpt-5-5/#and-some-peli...

Lends credence to my vibe-based assertion that GPT-5.5 > Opus 4.7 (and now 4.8), which is why I've cancelled my Claude plan. Opus 4.8 is them seeing it reflected in their own numbers and having to pull stopgap measures to avoid falling behind while they embargo Mythos.