There's is a section in Guns & Ammo called "Cooperisms" or some such. In the one last month, the section dealt with someone asking him to compare two different calibers, neither of which was .45 or 9mm. I'm not sure that I'll get the wording exactly right, but it was something to the effect of, "Such a comparison is useless. Either round, properly placed, is sufficient. Either round, improperly placed, is insufficient."
That said, I prefer .45 to 9mm. I wouldn't hesitate to carry a 9mm, either, though. I just wish I could practice with a .45 as inexpensively as I could a 9.