As you know, one of the main differences between the Alliance and the Horde is their sense of style. In fact, the question of what looks and feels good to players of either side may be one of the biggest areas of disagreement that actually exists between them. To a lesser extent, this sort of disagreement exists between classes as well. Warlocks give off a very different feeling from Paladins for example, and different people are attracted to each sort of "aura."
Like many players, my sense of aesthetics and beauty fits in squarely on one side of this aesthetic equation, and the other side can be rather difficult for me to understand. I play in the Alliance, and my favorite races are usually the ones that are "beautiful" and noble-looking in a traditional sense. To me personally, the Horde races are hard to relate to.
I do sometimes start up a Horde character if I have a funny idea for roleplaying him or her, but eventually something about them starts to bother me. Now that the Horde has prettier blood elves to play, I admit this helped me a lot -- I am gradually leveling up a blood elf alt in my free time -- but somehow being a blood elf in the Horde feels rather out of place, as if I'm not really part of the Horde because I'm not hunched over with a ready-to-kill look on my face.
For a long time I couldn't play a warlock either for similar reasons. The class just seemed inherently evil; summoning demons and stealing people's souls seemed wrong somehow. Even though I knew it's just a fantasy game, I still had no desire to mimic in the game something that would be abhorrent to me in real life. I often wondered: what is attractive about the look and feel of these characters to Horde and warlock players?
Now before you start pointing out to me the various inconsistencies in this sort of feeling (such as "how come you have a problem summoning demons when the whole game is about killing people?") keep in mind that this is not really an intellectual or moral issue. It's an emotional one. It's about that instant feeling you get of attraction or repulsion to something without even thinking about it at all. You just know you like it or you don't. In this case, I have one of those negative gut reactions to hunched-over monstrous player characters, as well as summoning demons and stealing souls, while many of you out there are deeply attracted to these things. While my eyeballs instinctively look at draenei or night elves and see "good," then look at trolls and undead and see "evil," many of you may look at trolls and undead and see "badass," as far as I can tell, then look at draenei and night elves and see... "goody-two-shoes" and "prissy" perhaps?
Now, nobody here actually summons demons or has rotting flesh or horns or whatnot -- far from it: you may even pray for world peace, volunteer at the soup kitchen, and sponsor a poor child's education. In real life (I assume) we all see ourselves firmly in the "good" category, or at least we "live and let live." I'm not questioning anyone's morality or suggesting that the Horde players really are evil or misguided at all. I'm just wondering, when you log onto WoW, do you like to pretend to be nasty, evil, or "ugly" in some way? Or is it not ugly to you at all? Would you insist on another word, like "badass" instead? What attracts you by the "darker" races and classes in the game? What repulses you by the "lighter" ones?
Update: I'd like to thank all our commenters for sharing their perspectives on this topic, and remind everyone that this is one of those posts where it's really important to read the comments below. I knew, as I was thinking about writing this post, that I had a certain bias based on my cultural background and upbringing, and actually one of my goals was to help myself get rid of that bias by understanding how other people thought and felt differently from me. I now feel that I have a much better understanding of what you all love the Horde so much, and I hope other readers who had thought as I did previously have gained a new perspective from you as well.
Also, I should have probably said earlier that I don't view all the Horde characters as ugly or evil looking. Mainly I haven't felt comfortable with the males hunching over and bearing their teeth a lot -- but the females have a few cases where they're actually quite adorable. I was playing around with some of their appearances a long time back, and I found some that were pretty neat. I even had a female tauren shaman for a while, and I might have gotten into that character if the guild she was in hadn't petered out (and if I didn't miss my friends on the Alliance side so much). She was a traveling "griot" or oral storyteller -- but she didn't get many chances to tell stories, unfortunately. If she had, I might have continued leveling her and come to understand all this through my own experience.