Claude has been pretty great. I stood up an 'auto-script-writer' recently, that iteratively sends a python script + prompt + test results to either GPT4 or Claude, takes the output as a script, runs tests on that, and sends those results back for another loop. (Usually took about 10-20 loops to get it right) After "writing" about 5-6 python scripts this way, it became pretty clear that Claude is far, far better - if only because I often ended up using Claude to clean up GPT4's attempts. GPT4 would eventually go off the rails - changing the goal of the script, getting stuck in a local minima with bad outputs, pruning useful functions - Claude stayed on track and reliably produced good output. Makes sense that it's more expensive.

Edit: yes, I was definitely making sure to use gpt-4o