I changed my perceptions a bit after repeatedly getting pwned by the brewfest dwaf boss, lol. He just hits too hard. DK, while regain hp fast, cannot deal with spike damage. I was dying left and right. So a good metric for tank for me is , whichever tank can handle him at ilvl 410ish IS THE BEST tank.
I totally agree with this entire comment. It's to late now (wait for next year???) but I have all 4 tanks (but three are at 85) and I'd love to compare a Paladin to DK on that boss. It's just a bit to burst-y for my DK, though I can kill him now fairly regularly. Though the reason I chose DK is the damage makes him almost a 4th dps'er in my groups, though admittedly post 5.0x my Paladin was doing good dps as well in Prot, I just like the aggro tools of a DK more.