Whether I'm looking at the M&S data, Fackler/FBI study or just about any source of information on the topic, I always come to roughly the same conclusion: handgun calibers can pretty much be lumped into three basic categories.
The first category is what I would define as backup/deep cover cartridges. Such cartridges include .22 Long Rifle, .25 ACP, .32 ACP, and .380 ACP. These cartridges, no matter whose data/conclusions you look at are not considered to be as effective as their larger brethren. The main advantage to such cartridges is that they can fit easily into small, easily carried/concealed guns. Cartridges of this type are, for the most part, best when loaded with FMJ or other non-expanding bullets because JHP ammo tends to not expand reliably and/or penetrate shallowly.
The next category is what I would define as service cartridges. Such cartridges include .38 Special, 9mm, .357 Sig, .40 S&W, and .45 ACP. These cartridges, when loaded with modern premium ammo, actually perform much more alike than they do differently. Muzzle energy is typically in the 300-500fpe range, penetration is usually in the 12-14" range, and expansion is typically 0.6-0.7". Premium JHP ammo is the best choice for these cartridges. These cartridges are the best choices for most people
The third category are the magnums. Cartridges in this category include certain .357 Magnum, 10mm Auto, and .45 Long Colt loadings as well as .41 Magnum, .44 Magnum, .454 Casull, and .500 S&W. With the right loadings, these cartridges are capable of delivering the same or greater expansion than the service cartridges, significantly deeper penetration, and, in some cases, useful fragmentation. The drawback to these cartridges is that they often require a large and/or heavy gun and nearly always have significantly more recoil than other cartridges do. Also, with just a few exceptions, magnums are pretty much the domain of revolvers. If you prefer a semi-automatic, you will have a much larger selection if you stick with service cartridges.
