This is like comparing apples to oranges IMO. Both very capable as a defensive weapon but the .44 wasn't designed as such. It was more to be used as a hunting round or defense against bears. Something I would not want to use the 45ACP for. IMO penetration of the 45 is horrible. It is definitely good enough as a man stopper but not too good on Mr Bruin unless you're lucky enough to get a brain shot without the bullet glancing off the skull. As far as a quick second shot - facing a charging bear from a holstered handgun you;ll be lucky to get even one shot off. I'd prefer to have a good hard cast .44 mag over a FMJ 45ACP