I've had the nock2it for about a year and really like it. I was lucky and a friend had one as well as a carter wise choice 3 finger, so I was able to try it before buying one. I had a Carter insatiable before I got the nock2it, but I found I prefer the 2 finger. The nock2it/wise choice also have the auto close jaws (only have to cock the trigger). On the insatiable and some of the other Carters you have to cock the trigger AND manually close the hook. Not a huge deal but I didn't like it.
If you don't have the ability to try a few, worst case you'll be able to sell the nock2it for close to what you bought it for.
If I was starting all over, I would seriously consider the Stan Perfex. The amount of adjustment is insane, so you're bound to find what you like. Comes with 2 thumb barrels, different length posts, and can be set up as a 2 finger, 3 finger, and 4 finger all in one release. So you can try it all and find what you prefer. They also have a complimentary tension activated Perfex, (similar to the Nock2it/Silverback).