Definitely frontend (it's what I do, every day, and I enjoy it), but I have a great deal of experience (over 25 years), writing some pretty robust backend stuff. I just don't enjoy it as much.
I haven't really used LLMs much for coding (sabbatical before LLMs got good at coding, now looking for work) but I found with chats that they are great at exploring well trodden territory but as soon as you go a little bit off the beaten path they flail horribly
They both do acceptably (but PHP better), as long as I don't push hard. The Swift that I get is ... meh, usually.
However, my PHP server, by design, is extremely conservative. It's meant to run on cheap shared hosting. I don't push the edges. The LLM seems to do a great job of respecting that, while still giving me good, modern, code.
The swift, on the other hand, has highly optimized UI (which also means that I'm not using SwiftUI). It shits the bed, when I push it.
I'm unlikely to run into many of the problems that (for example) the PornHub developers hit, several times an hour.
In that case, I benefit from folks like you, that allow me to have solutions that scale down to my level.