I was leveling thieving the other day, and I went from 55 to 60 in a short hour or two. Contrary to the above posts, I do not find blackjacking to be bad at all, you get into a routine. It just requires more clicks, but I managed to watch TV at the same time, so it's doable. I would try both and see what you like. Also check out Zarfot's Mega Thieving guide on the official forums. Keep in mind that blackjacking will give you far, far more xp than plunder will at your level. ~Kit