I switched to 15 lbs from 16 lbs 2 years ago, and I feel like I have a much looser armswing, less fatigue and can bowl for longer periods of time without seeing a decrease in ball speed or scores. Longer tournaments used to wear me out at 16 lbs., now with 15 I can go 15-20 games in a day if necessary. I think my carry has been a little bit better as well since making the move.
Matt