I shoot 3 under and the tab is much easier on my fingers, I get a smoother, cleaner release and I just seem to shoot much better with the tab. I've tried several, but ended up with the cheap cordovan one peice tab 3 rivers sell. Best one so far at about 9 bucks or so, I think.
the thing is, if you're gonna try it, make sure and fool around with it and give it long enough to really see if it's gonna work for you. Some guys try it for two shots and quit. That aint enough time. I tried it for a week, using nothing else, by then I had the different kinks worked out, and realized how much better it helped me shoot. That's when I switched for good.