Another reason is just distancing.. you might not be in perfect position in real life as opposed to training, of course, so minor adjustments to the punch's rotation can make up for that. If someone is in close, use an inverted fist; little further away, vertical fist; farther away, horizonal fist. And, of course, any rotation in between, like a 1/4th turn, 3/4th turn, etc.
If you're actually moving in to strike them, then it's just a matter of personal preference. Whatever you feel is more natural to you is best, IMO.
Edited by Inyo (11/15/05 10:08 AM)