That's about it. Mbin also provides a direct interface to the microblogging side of the Fediverse. Yes, you can already see posts from Lemmy on Mastodon and vice versa, but there's no way to actually microblog from Lemmy. Mbin has that.
I'm currently on fedia.io which is an Mbin, but the main reason I'm here and not on a Lemmy instance is personal preference. I wasn't keen on the Lemmy / tankie connection, and I liked the kbin/Mbin interface better anyway.
Unfortunately all the high traffic Fediverse groups (communities / magazines / what-have-you) have ended up on Lemmy instances, perhaps in part due to the problems the kbin creator had in his personal life and with the flagship instance, meaning people lacked confidence in spinning up their own instances and went Lemmy instead.
I never deleted my Reddit account precisely because I go in there periodically and find some of my comments became un-deleted, so I have to go back in and scrub them again to try to keep my content off the site.
That, and when I am Googling something and find a relevant thread on Reddit with the answer, I hate being defaulted to New Reddit, where half the comments are also buried and need to be manually opened to read more. Having an account logged in with the Old Reddit toggle is the simplest way around that (though wouldn't surprise me if someone made a browser extension for that).