RE: 40 S&W or 45 ACP?
Something to consider if you're going to be carrying it.The weight difference.For a long time I carried my Glock M-27 ,very comfortable to carry. I wanted to get a 45 ACP for a carry gun.I've always been a 45 fan.The little S&W 40 cal isn't any slouch either.
WellI got another Glock,this timea M-30. Very little difference size wise.Weight became an issue for me.With the 10 rnd mag fully loaded and one chambered it's just to heavy a gun to carry.I was constantly pulling my pants up.So my new 45ACP carry gun is now in the safe and the little G-27 came backout of retirement.