I play elves, in just about any game. And.. I started with Night Elves, but they actually got on my nerves (go figure...!)
I like Blood Elves better. Animations, emotes and aesthetically I find them pleasing.
I did find the Alliance to hold a lot of immature players, but I don't think it was the faction, more the realm I rolled on back then.
Like I said, I play Horde now and have found a few mature guilds on the realm I now play on.
I think either side will have any kind of person there is. WoW is quite big. I think it's a matter of how hard you look.
As the debate on which faction is more or less the 'good' or 'evil' faction...
Sure, I can understand people who'd say Alliance would the 'good' faction and Horde the 'evil' faction, but I don't see it this black and white.
I think every race in their respective faction has its own view on the world and this doesn't make the race good nor evil, on itself.
All races have done (or are still doing) something they could be less proud of.
Does that stop me from playing arrogant, power hungry, racist, magic addicted sons of bitches, myself? Hell no. That's part of the fun of playing a Blood Elf.