The only handgun cartridge which stands significantly out from the rest as far as capacity to stop a man-sized attacker, is the 5.7x28mm. This one has a reasonable ballistic potential to stop an attacker with a single hit to the chest. All the rest, from 380 to 45 to 10mm, require two hits to be effective. Yes, some will allege that rounds such as the 460 Linebaugh, the 50 Action Express, and the 500 S&W are exceptions. But these are not available in a weapon system that is practical for CC. So whether you carry a 9, a 40 or a 45, it makes little difference. All that matters is how quickly and accurately you can deliver those two hits to the chest of your attacker, and whether you can skillfully follow that up with a single hit to the CPU if that fails to stop.