Don't buy into the "Caliber Myth."
Ultimately, the diameter of the bullet fired from a handgun doesn't matter much. Modern powders, barrel manufacturing processes, and other technologies have pretty much moved all the major handgun calibers (9mm, .40 S&W, .45ACP, .38special, .357 Magnum, 10mm) so closely-grouped with regards to statistics that any argument from caliber to caliber is really just gun-geekery and nit-picking.
'Stopping power" of handgun ammo is the biggest myth perpetrated in the shooting community. It doesn't matter what size the bullet is, if you have bad shot placement.
You can shoot a crack-addled assailent with a whole magazine of .45acp Hydra-Shoks, and he will still be coming at you if you're hitting him in the shoulder, leg, and arm.
Or you can hit that same drug-crazed attacker with a single, high-velocity .22LR round shot from a short barrel handgun like a Walther P22, and if it is a headshot, stop him in his tracks. The fact of the matter is, .22LR is the most deadly handgun caliber in the USA today--more people are killed with that round than any other. Go ask your local coroner what bullets they most frequently pull out of DOA homicide victims. It will be .22lr, followed closely by .25 and .32 (about equal most places), with 9mm and .40 trailing a FAR distant 3rd and 4th. Of course, most of those homicides are gang-related (NOT justifiable defensive shootings), most are done at EXTREMELY close range (many are even execution-style) and most include at least one head shot and multiple body shots.
Then again, a well-placed #2 Dixon Ticonderoga pencil can literally drop an assailant in his tracks if wielded by a properly trained defender...
Don't get me wrong, I carry a full-size 1911 in .45acp, and I carry state-of-the-art defensive loads (Hydra Shoks or Winchester PDX1 Bonded). But I know that I can't expect a single round (or even three or four) to definitively stop an attacker unless i hit a vital organ, the CNS, or a major artery. And the attacker won't stop IMMEDIATELY unless I get a direct hit to the CNS...
I carry a .45acp because I know that even though I'm well-trained, accurate and competent, and my firearm is well-tuned and very accurate, in the adreneline-rush moments of defending myself (or my family) that first or second shot may not be as true as it is on the range. A large-caliber handgun will buy me more time to get a good clean shot if I need to pull the trigger more than twice, or even retreat to a more safe position, (or if in my house, to retrieve my 12ga shotgun). Big Caliber handguns are not a "guarantee", they are a "safety net" in case things don't go exactly as they should. The DO tend to inflict more damage when non-critical shots are scored, which whill buy you time to get a more "persuasive" shot if you need to. And the flash and loud report of a largeer handgun also brings with it a much more "persuasive" message than that of a smaller caliber...
Smaller caliber handguns can just piss off an attacker if you "miss the mark". They require much better shot placement to stop or deter an attacker.
In the heat of the moment of a defensive deployment of a firearm, you want to have as many aces up your sleeve as possible. Bigger guns have all four aces:
1) They are visually larger and look like you "mean business" before you even pull the trigger,
2) They tend to do more damage--even with non-critical hits,
3) When a critical hit is scored, they tend to be much more "decisive", and
4) they throw a big flash and a HUGE report from the muzzle, which looks scary as hell from the "business end", even if you miss...
You need to remember the history of the .45acp round and the 9mm round to really understand how they will work (and their appropriateness) in defensive use.
The .45acp was developed by John Browning as an answer to the ineffectiveness of the .45 Long Colt (and the .38 Special catridges used by officers) used against the Moro's of the Phillipines in the Moro Rebellion phase of the American-Phillipine War from 1899-1913. To prepare for battle, the Moro used a combination of body binding with leather, narcotics, and religious ritual to put themselves into an altered state of consciousness which left them insensible to injury. There are reports of Moro warriors being shot multiple times at close range with .45 LC and even .30 Krag rifles and still charging forward in their attacks on US Infantry troops. The .45ACP was DESIGNED, from the ground up, to stop drugged-up, heavily-clothed attackers.
The 9mm Parabellum (9mm Luger, [font="Verdana, Arial, Helvetica"]9x19mm, 9mm/08, 9mm P-08) was designed by Georg Luger in 1902 for use in a pistol he also designed for the German Military. As it was the general strategic policy for most European military organizations to adopt battle firearms that did a LOT of damage but didn't necessarily kill with one shot (a wounded enemy soldier takes a LOT more resources, and therefore causes more damage to the enemy than a dead one...), the original design for the 9MM Luger round was DESIGNED, fromt he ground up, to wound and injure, but not necessarily to be an effective "stopper"...
Modern 9mm rounds have ballistics that fall somewhere between .38 Special and .357 Magnum. The 9mm won't have the massive expansion factors that the .45acp will display, but it does penetrate well, and offers impressive terminal ballistic stats none-the-less.
The main advantages to 9mm over .45acp are increased capacity and decreased recoil.
The main advantages of .45acp over 9mm are larger wound channels/higher terminal ballistic specs, and (generally) less likelihood of over-penetration.
[/font][font="Verdana, Arial, Helvetica"][Rant]
[/font][font="Verdana, Arial, Helvetica"]I'm sure someone is going to get on here and start quoting the FBI's annual Ballistics Reports. I have the whole set from the 1990's, and was there for some of the range time (I was a NIJ contractor at the time, and involved in Body Armor testing), and I can tell you that the FBI criteria are pretty much meaningless for civilian defense purposes. They involve things like shooting through windshield glass, or a car door, or plywood, or wallboard, and STILL getting the sort of expansion and terminal ballistics that the FBI demands. That is an ENTIRELY different set of criteria than what most citizens will ever need in a defensive situation, and therefore, the FBI reports are, for all intents and purposes, nothing more than gun-geek wanking material for normal "civilian" citizens with regards to their information and it's applicability to our uses...
[/Rant]
Which should you carry?
My answer is "which you like to shoot, because the gun/round you like to shoot is the one you will practice with more often, and therefore you'll be more proficient with it. If you buy a firearm you don't like to shoot, it doesn't matter how good it's ballistic ratings are--if you can't shoot it effectively, it's just a VERY expensive piece of belt-jewelry. Modern manufacturing methods and materials, modern bullet design, and modern powder formulations have all made the tiny differences between the "major" handgun calibers pretty much a moot point. It all comes down to what YOU like to shoot, and what you are more likely to practice with, and what suits you the best (capacity, hand size, wrist strength, etc).
Again, I reiterate:
[/font]Don't buy into the "Caliber Myth."
