It's pretty much just a matter of preference now. With the changes to blood boil, thrash, thunderclap, etc all the tanks are fairly easy to macro and have comparable mitigation.

If you're going purely for a 5man comp, Warriors are far ahead of the others. Their mobility, ability to AoE snare and AoE stun are amazing. Shockwave alone is a massive mitigation tool and AoE interrupt on a 20 second cooldown. No other tank has anything comparable (unless you're fighting undead with a Paladin).