As a Paladin tank since BC, I'm a little biased against Druids (they were always the 'hybrid' that could actually do it all), so I'd vote DK :-P but that being said, it's really about what is fun for you. Both have good survivabity.

I know for me, it was what I was comfortable driving from (my Paladin tank). I currently use Paladin (Tank), Shaman (Healer) and Frost Mage (DPS) and it seems to work nice for me. For my second team, it was a little more fantasy based, so I have Warrior (Tank), Priest (Healer) and BM Hunter (DPS) - all Dwarves with names similar to that of The Hobbit.

Anyway, just my 2c. GL!