Thanks mcantar18c for your reply.
When I said, "I think that for consistent defensive carry or law enforcement purposes, .45 cal or .40 cal might be a better choice than 9mm" I meant that my belief is that those rounds are probably more effective at incapacitating someone with fewer rounds fired than using a 9mm.
Go look up Velocity/Energy numbers between common 9mm and common .40S&W loads... there really isn't that big of a difference, in fact most numbers are within 100 points of each other. Now take a look at this image. Can you honestly tell me that you see any significant difference? As I said before, ALL handgun calibers suck, and they ALL suck pretty much equally. The most effective "man stoppers" are shot placement and rounds on target.
Also, why the worry about how well you can drop them with fewer rounds? Instead of looking at it as "how many rounds will it take to drop this asshat?" think of it as "lets see how many rounds can I put in this asshat before he hits the ground." I can't put it any more simply than this: SHOOT THEM TO THE GROUND.
For people who put themselves in situations where using a handgun, outside of the home, is possible i.e consistent defensive carry/law enforcement then actions will be very closely scrutinized. Stopping the target, not killing them is the objective. This is my belief, and like many, might not be correct.
If you wake up in the morning, you've put yourself in a position where having to kill or be killed (with a gun or otherwise) is possible. If you do have to defend yourself, it doesn't matter where it happens... in your home, on the streets, or in the parking lot of a police station... everything you do will be closely scrutinized. Again, see my sig line on this. While the legal "after the fight" crap should not be ignored, it should not be something that worries you so much that it has effects your course of action in a situation. In a fight, when its kill or be killed, you do WHATEVER it takes to survive. The only unfair fight is the one you don't win. Train well, train often, and train to not only win, but to win as quickly and decisively as possible. Take down your enemy as quickly, violently, and efficiently as you can... whether this means turning him into a cheese grater with your CCW piece or opening up his arteries and airways with a shattered dinner plate, you fight to WIN. If you hesitate on doing what needs to be done because your brain is stuck on "oh shit am I gonna get sued for this?" you won't have to worry about it because you won't live to see it. Worry about the fight when you're fighting it, and worry about the "after the fight" after the fight.
I guess I am also a bit paranoid, this comes form working in the medical field where lawsuits and threats of them are routine.
Understandable
And as I said before though, if someone threatens me and I feel my life is in jeopardy, I will fight to kill. For home defense I use a 12 gauge shotgun and have 9mm pistols available.
Just a little tangent I want to go on here... a 12ga is great for home defense, no question there. But does it fit your specific needs? For me, a 12ga with birdshot works just fine (although I use a handgun)... but my buddy's primary home defense is a Glock, as a long arm doesn't work for him. Why? He has a 3yo daughter, and may need to carry her into another room to keep her safe... and he can't operate 12ga with one hand (slow to aim and no way to work the pump). I had never even considered this until he and I had talked about it. Point is, make sure you're accounting for everything you possibly can when selecting your HD gun... because there's always something you don't think of.