Claude Opus. GPT-4 gives sensible answers to basic questions, but takes serious persuading to produce useful output on non-trivial work. Opus can be used as an integral part of an engineering workflow and only takes 2-3 tries to get from ill-formed query to working product.This works particularly well when you copy the relevant excerpt from a project, dump it in, and say "Change X to Y, showing only the key modifications and where to put them". Typically it understands the aim and accomplishes t...