I think the only true way to find those answers is to use a robot, same lanes, different grits etc, BUT, once you throw in the human factor ( not releasing the exact same, not hitting the exact spot...you get the idea) then for a human I'd doubt the differences would really be much.
However, there is the mental part. If you THINK something helps, is better, then for you, the human, is it. To me it's similar to the argument of which is most important, drill or cover, depends on the person.
I'll agree there MAY be a small difference but I doubt MOST of us could ever really see the difference.
JMO
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az guy aka: R & L Bowlers Pro
rlbowlerspro@cox.net