Both sup and notmuch are clients that I've tried to use in the past.

Sadly neither would import my mail archive without crashing. Which is unfortunate because they look like they'd be pretty nice.

But in terms of advantages I'm finding the modal mode very interesting and the ability to open multiple folders. I guess via tagging regime you could emulate that in sup/notmuch, but I couldn't ever make them work on a decent size corpus of mail so I'm not 100% sure.

Right now I'd say the advantage is the lua scripting, which is letting me do interesting things even when incomplete.