It's interesting that we keep hearing that caliber doesn't matter, you can't tell a 9mm bullet wound from a .45 wound, etc., so why does everyone make expanding bullets?
If the bullets don't perform as advertised, you know you're going to get a .45" hole with a .45. That seems a lot more important than the potential for expansion of a smaller bullet. And, assuming that diameter really does matter, contrary to the "it doesn't matter" theory of handgun performance that is currently in vogue, I'll take the larger starting diameter.