I’ve always wondered why some people respond well to one medication but not to another, even if they’re both for depression. It feels like there’s no clear rule

Exactly. I found this article that explains the difference between the two—https://unitedrecoveryproject.com/rehab-blog/prozac-and-wellbutrin/. It’s a helpful comparison of how each one works and what situations they’re usually prescribed for. If someone’s considering either medication or just wants to understand their options better, it’s a good place to start