To be honest I never even thought about what finger the ball came off of last until working a few shooting clinics with Herb Magee.
He would pass around pictures of guys like Ray Allen that clearly showed the ball coming last off of the index finger. I've heard arguments both ways and I honestly believe there is no absolute correct way to do it. Everybody finds comfort on a different release--the important thing is that the fingers are spread and the ball rolls off of the finger tips last. My advice is the less thinking about it the better--just shoot the ball ensure you're repeating the same thing over and over. Find what works best for you and work on it every damn day.