I think a lot of it just has to do with how interesting the characters are to me, they feel like such real portraits and are more diverse.
HxH, as a random example, just has a collection of meatheads for the most part. Hisoka just isn't really... real to me. Or if he is, it's not someone I'd like to get to know. That kind of character captures the surface of a person without any of the real motivations or beliefs. Or rather the ones they have are quite limited. Same with Pitou, Pouf, and honestly can't remember the other guy..
Or Mereum, I mean he's a thug I get it, put him in a 50 cent video, whatever.
I don't really feel the same way about Euphemia or Suzaku, or Cornealia and Clovis, etc.