Debugging isn't the only thing - I used to use a standalone debugger years ago.

The key factor for me, is the ability for the tool to understand the codebase at some level. It needs to be able to tell me where a symbol is used, let me refactor that symbol (e.g. adding a new mandatory argument, or changing the argument order, or renaming the symbol) with as little extra work from me as possible.

Jetbrains tools allow me to do all of that (in PHP at least. I write about as much JS as I eat mud) where no others I've seen do.