In my opinion, yes, caliber counts. Of course, to be fair, so does marksmanship and tactics. Anyhow, when I look at a round of .45 ACP next to a .40 S&W and 9mm round, the size disparity always stands out. Try to chamber either a .40 or 9mm round in a .45, and they'll fall right down the barrel and out of the muzzle. Handguns aren't all that powerful anyway [compared to rifles or shotguns], so to me, it makes sense to go with the larger of the aforementioned trio. My philosophy about handguns follows the same logic that I apply to paychecks, steaks, hamburgers, locomotives, and women: Bigger is better!