I don't deny that a deep index/pistol grip of a recurve or hybrid or deep index on a reverse handle longbow, for example, might feel more comfortable and perhaps help one get a more repeatable grip than the straighter grips of an ASL. But those types of grips aren't generally found on a Hill/ASL longbow.
ASLs are by definition low wrist, fairly straight grip bows. Most builders just don't build very much dish or index into an ASL riser, so little, in fact, that it may be indistinguishable from a straight grip. I reexamined the two Hills I have. I think the grips may be dished, or perhaps straight. Just not enough difference to really tell. That's why the implication from my response was that it likely wouldn't make a noticeable difference to the OP going from one type to another ON AN ASL bow. Of course, there's a big difference in feel between a straight gripped ASL and a highly indexed/pistol gripped recurve or hybrid.
Tony, if I read your experience right, the big issue for you was the transition from a high wrist, pistol grip to a low wrist ASL. That would be fairly common, and it seems to me, that's really what the OP is asking as well. The type of grip on the ASL isn't as big a problem as the fact that the straight/low wrist grip is a big difference from the pistol grip he's shooting now.
For me, the differences in the three grip styles on an ASL make no difference. That's why I'd like to find out how and why for some others the index or dish grip works better than a straight grip on a Hill/ASL longbow. Thanks for the input. Any more?