I don't care about 'sectional density' or whatever.
2 in the chest, 1 in the head.
Calm Nerves x Accuracy + Energy Transfer = I win.
That can be accomplished with pretty much anything mentioned here so far including the .32 ACP. It'll take out a cerebellum/medulla oblongata as well as a .44 magnum, but less messy... and all the upcoming arguments about hole size and sectional density aside, the point is that the vital organ in question is destroyed resulting in practically instant death. That's the only argument I need, and science is on my side to prove it.
http://biology.about.com/od/anatomy/p/medulla-oblongata.htm
Sure, you'd almost have to be behind them and at point-blank 'execution range' to hit that target with any real certainty, but the point is that if you hit it, they drop like a sack of bricks. The brain won't discern what it was destroyed with. The cerebellum is the part of the brain that controls motor function, and sends electronic signals down the brain stem to the rest of the body through the medulla oblongata. Take out either point, and the body simply cannot function. No if's and's or but's, they are going down for the count. SHOT PLACEMENT. Energy transfer comes into play here when the bullet enters the cranium, it transfers it's energy into these vital areas, destroying them. You could argue that it's not necessarily energy transfer, but merely severing a vital connection, but either way, energy will be transferred to surrounding parts(see temporary cavity/wound channel), and even if you miss the main target, energy will be transferred, and at the least, interrupting function.
That type of energy transfer is true of all organs of the body. So whoever tells you that energy transfer isn't important in terminal ballistics, does not know of what they speak. And so therefore, it goes without saying that a larger bullet will cause more permanent damage. BUT a smaller, faster one may a larger temporary cavity, which is the result of energy transfer.
When you really break it all down, it doesn't matter as long as you can hit your target, and that your target is a point that will disable your aggressor.
As far as ignorant comments go, know-it-all's are in abundant supply throughout the world and enjoy sharing their limitless knowledge of BS with great pride and confidence.