well i have shot all three calibers in the same glock, and while i was not shooting specifically for accuracy, i didn't notice a lot of difference. I think this would be different the further out you get, as the higher velocity of the sig round i found let you hold to point of aim further out without adjusting for bullet drop.
I have an old generation two glock, one of the first things i did was put a barsto .357sig barrel in it. I was shooting milk jugs at 100 at the time. my impression was everything i pointed at i could hit it.
as to the 9mm i have heard to use 9mm mags, and a different ejector. supposedly if you don't the brass comes back in your face but i never had that issue either. I do know i use 40mags for the 357 and not an issue.
