[maxwells-daemon]

In my experience: one of Lean's main advantages is developer experience. It's convenient by design, with lots of automation to make easy proofs trivial. You do your work in VSCode or Emacs rather than some outdated IDE, and the server mode makes it easy(ish) to integrate with other software.

[sadfev]

I think CoqIDE is great and ProofGeneral (Emacs) is something all Coq experts use.

I have the opposite experience with Lean 4, the VSCode integration is horrid and documentation is awful.

The only good sources are papers for Lean4.

Granted I can go back to Lean3 but why would I?

[outlace]

But Lean4 is in alpha stage and there are no official stable releases yet, of course it's not well-documented nor polished yet. Lean3 works perfectly well and has everything you need.