Interestingly, I tried Sith first; created and leveled almost every class for the first week after the release. Even though it was the faction that I really wanted to be part of, I decided that I didn't like to be one. Pretending to be a light side Sith in a universe of dark sided ideas wasn't for me. I don't think the Sith community was any more mature/immature than the Republic side though, but again this was early game access days, things might have changed since then...