It really comes down to what kind of social media you are looking for. Pleroma and Mastodon are people focused (i.e. you follow people, not topics), while Lemmy focuses on communities/topics. Kbin is somewhere in between, you can both create post on an individual timeline and in communities, but Kbin is still relatively new.

Personally, I like Lemmy most (though Kbin might become interesting in the future). The great thing about the fediverse is that you can post with your account anywhere (with some limitation between different services) so it does not matter if you are on lemmy.ml or feddit.de or beehaw.org.