>>99363755kinda depends on what you want out of your Bat character.
Babs tends to be super perfect. Brilliant, beautiful, great fighter. Even if she's not the best fighter in the bat family, they're rarely ever going to go out of their way to show that. She alternates between being a perfect school girl kid to motherly experienced super smart lady. So there's a lot of ways you can project your fantasies with her.
Cassandra, the Buttercup of the group, honestly appeals to lots more emo types. She's specifically imperfect in a few ways, almost all of them social and mental. I don't need to say it but I think lots of people can relate to that.
Stephanie is kinda a fan girl try her hardest but is appealing cause she's one of the few people that (used to) seem happy about being part of the club. And she provided lots of perspective that, hey wait a second, we can be awesome people. She's constantly lower skill level than anyone else but that's never been the point, trying her hardest is often more relate able than being the best. Which is a nice counterpoint to your usual bat character.
