I use a pinky hole, and I can't say enough good things about it. When I started using it, it was to help me put more rotation on the ball, which it definitely does. In fact, I feel that the extra finger gives me much more control and repeatability with any release. I don't know if it officially helps put more revs on the ball, but it feels like it. It also helps tremendously to keep the ball stable on my hand throughout my swing (I don't use a thumb, so that's a much bigger deal for me).
I couldn't really tell you what the weight difference does reaction-wise, but I can tell you I've had three balls that putting the pinky hole in made the difference between needing a weight hole and not.
