I have spent a decade running mutt, a year running Gnus and a few months running mu4e before switching to notmuch on Emacs.

Mu4e is fine, but I found the interface slightly slow and awkward compared to notmuch. Notmuch's interface is really really good and quick.

Mu4e doesn't ignore underlying folders, which is cool if you have a very simple workflow. It's also superior to notmuch in the sense tags are stored in message headers, so they can easily be sync'ed across clients.