Feel free to bring up whatever sort of argument in favor of your favorite caliber between the 9mm Parabellum and the .45acp.
Not a fan of the poll options, and didn’t we just do this one in non-poll form? I like 9mm because it is cheaper, and especially because I don’t own anything that uses .45.
And of course, .45 is for sissies who can’t handle 10mm 
I have owned two .40S&W pistols only because the guns that fit my hand best were not offered in .45ACP.
.45 make’em bigger hole. Me like.
9mm is for anti-American pinko commie limp-wristed Prius driving granola eating Euro hippies.
9mm. Magazine size is everything.
I carry a 9 mm when I’m out-n-about. The main reason is that I *also *like to shoot my pistol when on the range, and 9 mm is a *lot *cheaper than .45. Plus it allows me to carry a compact weapon that can hold many rounds.
A .45 ACP obviously has a bigger bullet than a 9x19mm Parabellum; it has 61% more area. But how much of an advantage is that, really? I contend that it is only an advantage if you are an expert shot with dead-on accuracy. And 99.9% of shooters (including me and probably everyone else on this board) are *not *expert shots, hence there is really no advantage in going with a .45.
I have also seen a correlation between choice of pistol caliber and a shooter’s personality. Those that prefer 9 mm tend to be introverted, humble, and well-read, while those that prefer .45 tend to be loud-mouthed, chest-beating extroverts.
Are you a .45 man?
I’ve heard that people who own .45’s are compensating for a certain smallness somewhere else. 
A heavy .45 in your car will do you less good than a lighter 9mm in your belt.
Let’s see…9mm converted to standard measurment works out to .357 Well how about that. I’ll take the .357 mag then thank you very much.
I don’t believe in “knock down power” because that’s silly. I think that a 147 grain hollowpoint +P+ 9mm is going to impart plenty of kinetic energy at impact and expand reliably enough that in the end it’s more than sufficent as a self defense round. Plus there’s more of them in the gun, so were I to be in a stressful situation I’m not going to be screwed after 7 shots because I’m too busy shitting my pants to remember good form and sight acquisition.
I have numerous examples of each. Also a number of .40’s, a couple-three .357’s, and assorted pocket guns in various small calibers. I* do *happen to be an expert shot and any of the major caliber pieces will work just fine. The different platforms each have their own advantages and disadvantages, so I choose the gun/cartridge combo based on what I am going to be doing and what role the gun will play in it.
Caliber wars never have a winner, especially when they are pistol caliber wars. It’s like all the patients at the micro-penis clinic arguing about whose is most impressive.
.25acp is always a loser. Always.
The benefit of a larger bullet isn’t increased lethality or stopping potential per se. Stopping potential correlates very strongly with penetration, with the marginal threshold being at least ten inches of ballistic gelatin (roughly 8.0 to 8.5 inches in soft tissue), and the FBI’s criteria being a minimum of 12", with 14.5" being considered optimal. The 9mm Parabellum, .357 Magnum, .45 ACP, 10mm Auto, and (later) the .40 S&W all meet this criteria (save that the 115 grain 9mmP JHP does not quite get there when it expands). Given this threshold, effectiveness is really a matter of shot placement under the stress of real-world combat, not wound diameter.
While the volume of the permanent wound channel does increase with a larger round, the real advantage is that a larger diameter round will expand more reliably, and therefore deliver its energy to the target and not pose as much of a threat to anyone in the background. At this, the .45 ACP JHP is clearly superior–the large cavity virtually assures penetration even through thick clothing, and both the lightweight 185 grain and the heavy 230 grain achieve good penetration and reliable expansion. The 9mmP, and especially the 149 grain subsonic JHP, has a tendency to plug at the slightest provocation and act like a roundnose bullet, punching through-and-through and posing a hazard to the backdrop. This is not a theoretical issue; I know an officer who made a righteous shoot on one perp, but her 9mmP round punched through and plugged another target (still a ne’er-do-well, barely a week out of prison and on parole, but not carrying a weapon or threatening).
However, the 9mmP fits in a more compact package and offers more firepower than the .45 ACP, hence the popularity of the .40 S&W, a scaled down 10mm Auto that fits in the same “wondernine” envelope with double stack magazines with only a ~15% reduction in firepower. I don’t look to get into gunfights that require more than eight or ten rounds without resorting to something more substantial than a service pistol so I tend to like the .45 ACP, but then I don’t look to get into gunfights at all. I actually kind of like the ballistics on the .400 Cor-Bon, which is somewhat flatter shooting (although it doesn’t truly replicate the ballistics of the 10mm Auto despite what proponents claim). Super compact .45s tend to be either too light to be manageable, or have a retardedly short barrel, which attenuates muzzle velocity as SAAMI spec pressures require the .45 ACP to use a slower-burning powder.
Both the .45 ACP and 9mmP can be found in cheap surplus ammo, although the 9mmP is cheaper by far, whereas the .40 S&W and .357 Sig (a .40 S&W necked down to a 9mm bullet) are way expensive for regular practice unless you reload, so there is a good argument for taking up the 9mmP and getting a lot of practice versus a larger round that is marginally more effective with significantly less practice. I would personally carry a 124 grain SJHP if I were going to carry a nine, and make certain I could reliably pop two rounds in the x-ring and one in the head.
But it is all ultimately it comes down to penetration and shot placement, and either the 9mmP or .45 ACP (or any round in between) can make the penetration threshold. So carry what you can shoot accurately, and train for combat-like conditions if you are going to carry for defense.
Or better yet, just avoid situations where the issue might even come up whenever possible, and die a peaceful death.
Stranger
I carry a light .45 in my belt. Problem solved!
You speak too soon, Grasshopper. John Moses Browning hisownself designed the .25acp to give more reliable function in (what used to be called) vestpocket automatics than the .22lr. So, if what a fellow is after is a really tiny automatic pistol that actually works reliably_think of the absolutely adorable Baby Browning_then the .25acp is the clear winner. It will feed more reliably than the rimmed .22lr, it will ignite more reliably than the rimfire .22lr, and will be more durable than the heeled-bullet construction of the .22lr. Finally, and this is important, it will give better performance than the .22lr when the two are fired from barrels of the same length.
If you have no hankering for a vestpocket auto, all this is moot, of course. But back in the long long ago, lots of folks carried tiny autos in anemic calibers and got by with them. People were, somehow, simultaneously tougher and wimpier back then. They were tougher because they could get by with such unimpressive guns, but they were wimpier because they could be killed with the tiny bullets. Not like today’s titanium-skinned, meth-fueled murder machine criminals. A fellow would be a fool to venture out today with anything less than a .50BMG stoked with armor-piercing incendiary rounds. And that’s just to go to the Circle-K for milk and smokes. Going to the mall requires *serious *weapons.
The one hanging from the bed post is a 9mm, so I guess that one wins. But then, I own a couple of .45s. Including a Hardballer Longslide, which makes me feel like Ah-nold whenever I take it to the range. But the one in the nightstand is a Highway Patrolman.
Guess I’ll choose 12 gauge, which is in the closet.
Note to self: when attacking the silenus household, utilize a standoff weapon. Preferably the M119 105mm howitzer or larger.
Stranger
Ha ha. Silenus uses a shotgun that is ashamed of its sexuality. Ha ha.
All my guns are comfortable and open about themselves.
I carry a light .45, but I have no particular opinion on the 9mm v. .45 debate. It’s more about the shooter than the weapon, anyway.
I’ll split the difference with you and say that the absolute minimum that’s acceptable in pimp gun configurations would be .32acp, but these days there’s no reason that the minimum can’t be .380acp since Ruger introduced that adorable little LCR.
I know, I know, the .25 in your pocket beats the .475 Linebaugh at home in the closet every time but if the issue that you set out to solve with the chambering is to make a better .22 that’s fine, but .22 isn’t a self defense caliber in any sane discussion.
The longslide is a dream gun of mine, one day I’ll have the money to not only buy the gun but to get it plated so it doesn’t spall on me. The Highway Patrolman is a great gun, my pre 27 has been retired from nightstand duty and was replaced by the much more boring but useful Glock 17.