I like being the protector. I don't mind the grief I sometimes get.

I love me some speed runs but if I don't think my healer (I pug a lot) can handle it, I go easier on them. I like being the guy that gets to make that choice, because I am the quintessential Nice Guy Tank. I will get back up and go at it again and get some newbies the win.

As DPS, I don't feel like I have very much sway over the battle. I can't do much to really help the group and I dislike that. Tanking or Healing lets me do that.