It depends on your skill. DPS is more brainless and less mission critical. If you screw up as a tank you ruin it for everybody in the dungeon.
If you go the tank route, I recommend just watching a youtube guide of the duty you are about to go on. It'll take 5 minutes but it'll ensure a much smoother run every time. If you don't feel like making that commitment, then DPS would be your better choice.