Death knight druid or paladin

can you guys pls tell me which of them is best at pvp, and at tanking in PVE?
thanks everyone :)

Well, it's like a personal choice, I like my dk for tanking and druid for resto pvp.
Maybe go for a druid since bear can easily tank with feral pvp gear and doesn't need def cap (got the talent).

Death knight druid sounds like a strong class on paper, but I'm not sure its possible, so I guess that leaves paladin.