One thing that always struck me as odd was the disparity between the level of the Horde guards in Tarren Mill (level 60-ish elites) and the Alliance guards in Southshore (level 40-ish non-elites). Stealthy Horde players could slip into Southshore, kill NPCs and lower level players with little regard to the guards. However, any Alliance player attempting to do the same in Tarren Mill would be in for a rude awakening if he or she was spotted by the guards.
More recently I've found yet another difference between Horde guards and Alliance guards. I'd been testing characters on the PTR, and stopped by Stonebreaker Hold in Terokkar Forest with my undead rogue. When I dropped into stealth, I noticed that many of the NPCs, guards, and peons were able to see through stealth (they had that stealth detection icon floating above their heads). I remember being in Allerian Stronghold with my own human rogue and not seeing anyone that could see through stealth. I decided to sneak in (if I could) to see if the Alliance had trained their guards to detect stealth, and to my surprise, they hadn't!
The argument about whether or not Blizzard favors the Horde over the Alliance popped into my head for a moment -- I know it's old hat, and players from both sides have slung accusations and "proof" that Blizzard favors one faction over another, but I've never seen anything definitive.
I'm not looking to start up that old argument, but I am wondering -- has anyone else has noticed a situation like this, where the Horde's town guards are clearly superior to the Alliance's guards?