People. Energy is energy. Period. You know that E=MCsquared thing. Many of you keep making unrealistic comparisons. IMO..for the purpose of a person to person defence load...Throw caliber out the window, except to say start at .380 and go up from there. Only minor exceptions would be .22 mag or 327mag. But in general..Now think of it like this: any load that generates between 300 f/lbs and 600 f/lbs is where you need to be. Once you get up around 600 f/lbs. and above things start to change, having nothing to do with caliber. It is energy delivered to target. An Apple to Apple comparison would be .380, 95gr at 1000ft/sec vs .243, 95gr at 2960ft/sec. Tremendous difference in energy. Exact same mass at 3 times the speed. In the 300-600 ft/lb range there are no Magic One Stop Bullets.
Pick what you are comfortable shooting and run with it. .45 is way overrated and outdated. And....proven many times...faster bullets expand better, transferring that energy to target. Oldest, hottest topic on any forum. Best wishes