The Horde was branded the "cool" faction by fat, acne ridden, basement dwelling, lifeless nerds. The number of points in damage they can do is directly proportional to the number of times they spend masturbating alone in the dark. They supposedly win every PvP fight, and are always the first to kill the big dragon. (Bullshit)more...
PvP: Top arena teams are almost always consisted of Alliance players, and if you are one of those faggots who think that BG's take more skill then arena, most battle groups are balanced in terms of Alliance vs Horde win loss ratios. In actuality the horde dominates just as many battlegroups as the alliance. But hordies love to brag, and thus are "L33T"
PvE: As for PvE the number one alliance guild is only a hair behind the number one horde guild. But your chances of getting into ANY of the top guilds in the world is slim to none, unless you cast away that useless thing you call a life into the gutter. In PvE, Alliance vs Horde progression is completely dependent on your server.
Personality: There is a common misconception that all Alliance players are 13 years old, but those people make up a small portion of the alliance. Although the horde is generally more mature then the alliance, that isn't to say that you aren't going to run into your fair share of retards. People on the horde tend to believe they are the best at everything, and never take anyones advice, regardless of how good it is.
If you are a girl you will be hit on/molested constantly.