Re: Alliance in WoW - I've gotta rant :D
Here is the skinny on the two sides. Horde tend to be a bit older in age and tend to be more relaxed gamers. Alliance tend to be more flashy and younger players. That being said the difference isn't huge but it is just enough to be noticable, of course there are exceptions on both sides.
Keep in mind that at this point in the game, many players are playing alts on the other side as they grew bored with their original side.
What server are you on BTW?