We're taking about handloads now
Man, I'm out of it for a bit and everyone gets delusions of grandeur
Seriously though, use what you like best. The 45 has been killing people longer, but the 40 has been working hard to kill people too. I personally wouldn't want to be shot with either. Come to think of it, I'm not sure I would really care which you shot me with. I'd probably be pretty irate either way.