After playing all 3 kinds of tanks, I can safely assure you that any tank can be multiboxed.

For solo play, I prefer tanking with a warrior. No mana, very manuverable, high mitigation making gearing up easy, way more control than any other tank, and my favorite tanking ability in game - spell reflect. Tanking with a warrior is challenging, probably the most stressful thing to do in game, and if you thrive on it, it's AWESOME. For boxing though, warrior is the poorest choice. He's just got too many abilities to use to build up aggro. There's the SS>dev>dev>revenge rotation, which I spose you could macro down to one button, but for true multi-mob tanking, you need cleave, TC, heroic strike, cuncussion blow, shield bash, spell reflect, taunt, stance dance macros, intercept/intervene and probably much more I'm forgeting off the top of my head. If you have a group of mages or something, warrior will do better than fine if you can chain cc adds and concentrate on tanking only one target at a time. In the xpac, warriors get a few more tools to do some insane aoe tanking, but they won't get any easier to play.

Paladins are kindof the retarded stepbrother to the warrior who's been dipped in superglue. Solo play, paladins are boring as hell. The only fun I have with mine is seeing how many mobs I can tank at once. Toss the shield, holy shield>consecrate, and you've got add control covered. For single target threat, it's as hard as judging righteousness every cooldown, that's pretty much all there is to it. It's no wonder pallies are the prefered tank for mb, because they can be effective with as little as 3 buttons. And as long as you have salv on the group, you will not lose aggro. I've held aggro with a measly 200 spell damage on ele shaman who put out over 1600 dps on a boss. It's much harder to gear a paladin, you'll always be lacking mana or will be too squishy till you've got a bunch of badge gear, but once you got one settled, it's all gravy.

Bears are the inbetween tank, don't quite have the AOE capability, but don't have an overabundance of buttons. Thier survival is through the roof though and by far the easiest to gear up.