I'm leveling a prot warrior right now (level 20 woot woot) and loving it. However my main is a prot paladin that I tank ICC25 with. Our other tank is a Warrior and, like Matt said, the only real difference is that he uses Exp/Stam gems in his red sockets rather than Agi/Stam like me (as Paladins can get the expertise they need from Pillars of Might + the SoV glyph). We both use the same shields, neck pieces etc. The only other differences gear wise is that Warriors use guns as a stat stick and Paladin librams are more like passive trinkets in a sense. For the most current content, Paladins won't shoot for their four piece T10 set bonus until they are hitting ICC25 Hard Modes (and even then there are a few pieces that would warrant using 3 at the most) while a warrior would push for their four piece.

I've often logged on and looked at my gear and if I wasn't a Blood Elf (horde paladins ftw) there would be very little to distinguish me from a warrior with my Boneguard Commander's Pauldrons, Pillars of Might, Cataclysmic Chestguard and the other warrior themed non set pieces from ICC (I have my 25 man T10 helmet graphic turned off cause it looks ridiculous with my pig head shoulders).

So really the differences are minor, we both gear for EH, great threat stats are Exp/hit (though paladins need less Exp through their glyph), we both use shields/plate/1H tank weapons. Really our difference are in how we tank and our small niches (and that Paladins are better, at least until I log onto my warrior, then warriors are the greatest thing since sliced mana biscuits)...