I agree that part of the difference between grips and not will always involve personal preference, but even that would be the result of some scientific or tangible difference between the two styles. You even eluded to it in explaining the slightly different way the fingers would be placed in the holes depending on whether grips were included or not.
Tonight I used both (grips and no grip balls, and think I MIGHT have gotten a little closer to determining why I have success in certain situations with the grips, and then on another night, am more comfortable without them. It seems that when I have the inserts/grips, that I am able to keep my fingers in the ball a tad longer, which produces a bit more lift and rotation.
That would be a good thing (at least for someone like myself who is more speed than rotation dominant) in MOST conditions, but I discovered that when the lanes are drier, or have stronger backends, that this causes me to be more erratic. 2 or 3 ---or 4--- beautiful shots to the pocket and lots of pin action and carry. And then, the next shot is held for a second too long, or thrown a shade slower, or ....or something, and ends up WAY off target. With the inserts/grips, I tend to be more consistent, with the main problem being that the ball sometimes leaves my hand before I have had a chance to put some rotation and lift on it.
Tonight, I had some success AND failure with both gripped and un-gripped balls, but what I finally think I have found is that I just need to wait a second or so longer before starting to lift/rotate the ball when not using grips. As long as I force myself to wait, I deliver a nice consistent, predictable and reliable shot to the pocket. If I start turning or lifting too soon, the ball either hits the pocket but hits flat, or just goes off target, cause I didn't hang onto it long enough. With the grips? I get better pin action and apparent carry, and can frequently string together a bunch of strikes without having to be that precise in my deliveries, but can also easily roll a completely awful shot at anytime ----just by hanging on to the ball a second too long.
Anyway... tomorrow, am going to stay with no-grips and try to force myself to delay the turn/lift part of my delivery for a second or so, and see if I can get something going.
In short... I seem to be able to string strikes together more often with the grips, but without them, I seem to have an easier time keeping a string of strikes going once started.