Claude is faster on inference. Sonnet is cheaper per token. Neither handles latency spikes gracefully.
Honestly, I've been running both in parallel for the last month on some payment reconciliation work, and the gap is smaller than people think. Claude 4.7 gives you better reasoning on edge cases (malformed transactions, weird timestamp formats from legacy banks), but Sonnet 4.6 is almost there, and the cost difference adds up fast when you're processing millions of records. For us in Lagos, latency to Claude's servers is already iffy, so shaving 200ms off inference time doesn't matter much if the round-trip is 800ms anyway. The real win is that both are way more consistent than they were six months ago. No more random hallucinations on structured data. I used to have to triple-check every output. Now I spot-check maybe one in fifty.
The thing that bugs me is neither model actually admits when it doesn't know something. They'll both confidently spit out a schema that looks right but has a subtle bug. You catch it in testing, sure, but for background jobs that run overnight, that confidence-without-accuracy pattern is dangerous. I've started adding explicit sanity checks in post-processing because I don't trust either model to error gracefully. That's not a model problem, it's a how-we-use-them problem. But it matters. Use them for logic and reasoning, not for sure answers.