the Carter 2.75 and the Tru-Ball Sweet Spot are both good releases but you need to try and get someone who REALLY knows how to shoot them to help you learn how to shoot them right...80% of guys that have Backtension releases shoot them wrong
I use the T.R.U. BALL Sweet Spot 2 (3 finger). I would definitely recommend this release, but have to agree with xXx in that knowing how to shoot correctly with back tension should be your first order of business. I read
Core Archery: Shooting With Proper Back Tension by Larry Wise and got some individual instruction from a couple of pros at my local shop. I would have been lost on what to do without them. However, if you've got BT down to a science then just find that release that fits you right and that you feel comfortable shooting with. The pros that helped me shoot both Carter and T.R.U. BALL releases. When I last spoke with them, they said they were moving away from their releases with thumb triggers, because they found themselves using the trigger and not back tension to release the string. Just something to think about before your next purchase. Cheers!