Originally Posted by vampireuk
Extra armor, extra defence, extra resistence to stuns
All in the first 2 tiers of the tree.
Cheaper sunder armor: If you have trouble w/ rage while tanking, you're doing something wrong, especially if it's in MC.
15% increased threat generated in def stance: Probably useful on ragnaros only as it involves a lot of aggro wiping, the tank regaining aggro, and maximizing DPS, but our tanks have no problem with that, so it doesn't make that much of a difference.
I'm not saying that some warrior going arms/fury/prot will tank better than if he went protection, but if you PvP at all, going 31/5/15 is much more effective and you still tank almost as good as a full protection warrior, and therefore would recommend using that. Gear makes a bigger difference than protection spec when it comes to tanking.