I play Alliance now, but I started out as a Horde player. I have pride for both factions, but I think I will always have a preference for the Horde. They're very diverse to me. The Alliance seems so humanoid-centric: You have humans, you have dwarves (who are squat humans), you have gnomes (who are even smaller humans), and you have worgen (who are shape-changing humans). It could just be cynical me.
I think my most favorite thing about the Horde is their symbol; it's unique, it's bold, and no one outside the game will know what it is if they don't play. It's a great emblem for a shirt, jewelry, or body art.
I just can't get as excited about the Alliance symbol. I love cats large and small, don't get me wrong. But it just looks like it belongs to a family crest or on a shield. I wouldn't sport it on my clothing or pay for the body art. That symbol just doesn't evoke the same pride as the Horde symbol. To be honest, I like the Argent Crusade or Silver Covenant symbols more than the Alliance lion crest. Granted, the Alliance get the lion mount, which is awesome ... but that's going on a tangent.
Do you take pride in sporting your faction symbols? If not, what changes would you propose to make them better? What are your favorite faction symbols in WoW?