I shoot mine both as the .40 and the 9mm. Beings 9mm is more new to me than any of the other calibers I own. My .40 groups are better as far as accuracy and time is concerned.
It just depends on how much u shoot it. Once u get use to the bigger calibers. Those smalls one dont seem to give u much of an advantage. Excpet maybe an extra round or 2. And in my case, as bad i shoot the small caliber. I'd need that extra round or 2 lol.