Let me begin by stating that I am a devotee of both Fackler and Marshall/Sanow, although I find Fackler to be far more credible based upon the sheer depth of his experience and the soundness of his science. I also favor firearms that have been used by the U.S. military, and two of the first pistols I ever tried were Colt Government Models (a Series 70 and a Series 80), which I found fit my hand comfortably and shot tolerably well. The Government Model and its variants are typically chambered in .45 ACP, which also influenced my caliber selection.
.45 ACP was the chambering used by the U.S. Army from 1911 through 1986 in the M1911 pistol. Through two world wars, Korea, and Viet Nam, it acquitted itself wonderfully, saving many a G.I.'s life. It has a very long service record, and there has been a lot of data collected on its performance (although, admittedly, much of this data is anecdotal). Brass for practice ammo is easy to come by, although it is currently somewhat expensive due to the Army's 1986-199? run of using the Beretta M9 pistol (in 9x19). Now that at least SOCOM has once again standardized on .45 ACP, hopefully once-fired brass will become cheaper.
As cited in IV.F.1, ``The Facklerite's Case,'' one determinant of incapacitation or ``stopping power'' is the amount of tissue that is damaged by the bullet. Shot placement is the primary determinant, but given less-than-perfect aim (and under stress, most of us will be off somewhat), how likely is a mid-torso shot going to stop the attacker before he can hurt me? The Facklerite article cites MacPherson's figures for the amount of tissue damage that is to be considered ``adequate'' to incapacitate an attacker given a nonvital wound. That figure is 30 to 40 grams of tissue. The .45 ACP cartridge, when a JHP bullet is used, resulted in 55 grams of destroyed tissue, which is ``more than adequate'' per MacPherson.
.45 ACP bullets are the biggest and heaviest of all of the most popular self-defense calibers. Typically, the lightest bullet used is 185 grains, and the heaviest is 230 grains (I favor 230 grain Hydra-Shok). Sheer momentum appears to assure adequate penetration for the crush cavity to extend to a vital organ (hence the large amount of tissue damage cited above). Velocities are lower than that of 9x19 and .40 S&W, but that is not a problem. As Fackler has repeatedly stated, kinetic energy is not a good determining factor of stopping or killing power. The only thing you can trust is the size of the crush cavity coupled with good shot placement.
I look to Marshall and Sanow purely to bolster my sense that .45 ACP is the best round for the job: acknowledging the statistical problems with their sampling methods, .45 ACP comes out on top in one-shot stops when the hit is in the mid-torso. Yes, this is an unrealistic statistic, but it gives me some reassurance nonetheless.
What all this boils down to is this: if I ever find myself drawing my gun to save my life, I want to be absolutely certain that if I do my job and put the bullet in the right place (or at least close), I'll have the absolute best tool for stopping my attacker as quickly as possible. My sense is that 9x19 is marginal for this task, .40 S&W is better, but .45 ACP provides that extra margin that gives me peace of mind. The empirical differences are probably in reality pretty small provided that the shooter makes accurate hits to vital areas, but the subjective feeling of additional self-confidence in the case of incapacitation from nonvital hits cannot be discounted.
That, and I really like the way a .45 feels in my hand.