If it's a carry gun, alloy is the way to go. If it's a range gun, steel. It's that simple. As for caliber, if it's carry, why not go with the the ballistics of a 45? The only arguments against the 45 are recoil, which in an emegency, you're not going notice or remember. You give up a round or two in capacity, which just means you need to make every round count. If it's a range gun, shoot whatever you like. All of my 1911's are range guns because condition one gives me the willies. Yes, I know all the arguments for how safe it is but it's still a mechanism and Murphy's Law still applies. For carry, I'll stick with my Shield Plus in 9mm but if I'm feeling really paranoid and follow my own above advice, I also have a Shield in 45.