Although I've been pretty scarce on the forums of late, I always enjoy Mikey's take on topics such as this one, and for the same reasons I value Fairbairn-Sykes-Applegate. Methinks they have "been there and done that," whereas my personal experience is limited to shooting some deer, some milk jugs, as well as reading a lot and thinking about what I read. Luckily, I believe that we can actually learn a lot that way--I don't need to personally touch a glowing hot stove burner to believe that would really, really hurt!
I love to read about all the options, inches of penetration, and newfangled means of trying to solve a problem that we've faced for hundreds of years: how to use a handgun to get a BG to cease and desist, preferably sooner (-est) rather than later. Nonetheless, I must admit that I think LocnLod is dead right when he states: "With handgun rounds stopping power has more to do with the mindset of the person you shoot than what you shoot them with. As long as the bullet has enough power go do deep enough to hit a vital organ, spine or brain, apply and repeat as necessary."
Sykes said very much the same thing in Shooting to Live with the One-Hand Gun back in 1942, and while expressing a preference for big bullets that moved as fast as possible, he emphasized that his extensive experience in Shanghai had convinced him that no caliber was magic. Granted, his police/military choices were limited to non-expanding bullets and he would have preferred expanding ones, but he simply saw too many cases where small bullets worked, big ones didn't, and vice versa. Accordingly, he limited his recommendations to advising his readers to select a serious caliber--which he essentially defined as .32, .38, .44, .45 or approximately those sizes--and learn to shoot it with all the speed and aggressiveness of which the shooter was capable. Although he obviously understood that shot placement was important, his experience convinced him it was most important to shoot first, hit as soon as possible, and fire in bursts of 2, 3 or more shots. He found that 50% hits anywhere on the target generally proved "adequate to the purpose in view," when delivered first and aggressively.
I usually carry a .38 SPL or .38 S&W revolver, but sometimes carry a classic Remington 51 in .380 caliber that I can point shoot very rapidly with one hand and score well-placed hits at ranges up to 25 feet. (Longer effective range in deliberate fire, but I don't think that's likely to be relevant to my specific purposes.) It's loaded with Hornady Critical Defense, although I've also carried it with Speer Gold Dot or simply flat-nosed Winchester ball ammo. I'd be very comfortable with Buffalo Bore flat nose lead, but can't afford to practice with it much and also hesitate to use it in a classic firearm. Once I start reloading and casting for this caliber later this year, I'll try to find a flat-nosed lead bullet of 100-120g that my Remington likes, shoot it a lot, and then carry that.
Given my situation, when I carry concealed I expect to face a prospective opponent up close, and I plan to do my darndest to shoot fast, first, and keep shooting, and I am betting that multiple rapid hits gives me pretty good odds of winning. Anything less reduces my chances.
At home I have a .45 ACP and a .44 SPL, because I view the tactical situation a bit differently. I still intend to try to shoot first, fast, and multiple times if I ever need to use it in a crisis.