Well, here is my two cents:
1) Despite being a small-ish guy, I can still pretty easily conceal a 4-5 inch barreled, double stack handgun.
2) Larger guns are more comfortable to shoot than pocket pistols, which means the likelihood of practicing with them goes up, which means you will be better with it, which means your 3 shots are going to count more. But at the same time, if you are less likely to carry a larger gun than a smaller one due to comfort and concealability... well, you can't have your 3 rounds if you don't have your gun.
3) The reason why soldiers carry full-size guns is because they don't have to conceal them. If the Hague Convention or the Geneva Convention required warriors to dress in civilian clothes and conceal their weapons, we'd probably be seeing a lot more .32 and .380 military guns.
4) We see that three shots is the "average" self defense scenario. But the average trip in my car is only a few miles. I still try and keep my car above 5 gallons (1/4 tank), even though two cups of gas will get me most places I go and back again. One of my professors pointed out that the "average" American has one ovary and one testicle, but no such person really exists. Anybody who has studied statistics knows that an average is a white lie, and can be misleading. I read somewhere that the vast majority (>60%) of encounters involving guns for self defense do not even involve shots being fired. Simply displaying a gun will make the cowards run. But I am not going to carry an empty gun, or a single shot.
5) The division between "hunter" and "hunted" seems really forced here.
a) Assuming that there is only one predator can be dangerous. Lookouts, accomplices, back-up men; these are all common enough that having more than three shots might help out. Muggers and predators are usually cowards, and it is not too much to assume that a coward will run in a pack (as some predators in the wild do).
b) Barrel lengths trade-offs for precision/maneuverability I get. That is why I don't carry around a rifle. But difference of less than two inches (2" snubnose vs. 3.9" CZ 75 P-01) is not going to make much difference in maneuverability.
c) The best gunfights are the ones that don't happen. If you can avoid one by running away, that is great. But running is what prey does. And the best way to attract predators is to act like prey. Thugs don't want a fight, they want a victim. Running to get out of a situation only convinces your assailant that he doesn't have to worry about fighting you, only chasing you down.
6) I've met people who have tried to get rifles and shotguns on their CCW (mainly as "truck guns"). If they could carry one around in public, they would. If short barrelled rifles and carbines could be carried legally and openly where I live, I'm sure there would be people who carry them. If for no other reason, most predators will be less likely to attack if they know you are armed.
7) I know people who carry pocket guns and people who carry full size. Just from my experience, most of the difference in what they carry has to do with their outlook on self defense. People I've met who carry pocket pistols tend to see a self defense scenario as practically impossible. I do not want to go into how accurate this assumption is, but I've noticed that people who carry larger guns tend to perceive self defense situations as a more immediate threat. One of the other differences I noticed is that people who carry pocket pistols tend to run in groups more than people who carry larger framed guns. This is just a generalization, and I'm sure there are plenty of exceptions, even among the small sample of people replying to this thread. But maybe we have an inherent tendency to be more cautious and be more heavily armed when we aren't with the herd.
8) I own a Glock 37, which is a .45 GAP. Most people will scratch their heads and ask "what will a GAP do that an ACP won't?" Well, the answer is, it can fit in a smaller frame. Other than that, the GAP is is considered by most to be redundant. I could easily ask "what can a pocket pistol (or other conceal pistol) do that a "duty" or "combat" pistol can't?" The answer is similar. And for those who carry the larger pistols without issue, having them carry smaller guns is like trying to convince somebody with larger hands to replace their .45 ACP chambered guns with .45 GAP.
9) What you can consider a carry gun depends on how big you are. I knew somebody who knew somebody who knew somebody that was 6'8" and 300+ pounds. The dude carried a Desert Eagle, and he made it look like it was no bigger than a 1911. Hey, if he could swing it, by all means, go for it. I doubt anybody was going to be picking a fight with him, anyway. On the other hand, if I carried a Desert Eagle, I'd probably universally be considered an idiot (and rightly so).
10) We live in a world where crime rates are going down in most places. Hold-ups are becoming less likely for most of us. In fact, if you took away the crimes in the solid-blue murder pits like Chicago, Detroit, and the other inner-city Democrat strongholds, the US would have an incredibly low violent crime rate. This means that not only is the crime rate going down, it is becoming more concentrated, which means you can avoid these areas altogether. However, we also see that indiscriminate, mass shootings are becoming a more realistic threat, and we see that they happen in a wider range of social and economic zones. Protecting against a nutcase out on a suicide mission is now a bigger consideration in carry gun choice than it used to be. The people our soldiers are fighting in combat and the guys we might end up protecting ourselves and loved ones from are more similar in tactics, equipment, mission, and mindset than they used to be. If I had to defend myself from one of these guys, I wouldn't want to be stuck with a Beretta Tomcat.
In conclusion, I realize that guns are tools, and different jobs require different tools. You wouldn't want a hammer if you needed a screwdriver. But carrying a Sig 229 or a Glock 17 instead of a S&W Shield is more like putting a long-handled screwdriver in a tool kit when a short-handled screwdriver will do. Not exactly a sin, in my book. The question of what to get for a carry gun can be boiled down to four questions;
1) What is the largest size of gun that is concealable on your person?
2) Not going any larger than the answer from #1, what is the largest sized gun you are willing to carry with you all the time?
3) Not going any larger than the answer from #2, what is the largest sized gun you are comfortable/confident shooting?
4) What is the smallest sized gun you are comfortable/confident shooting?
Whatever guns lie between answers to #3 and #4 are the guns that you should look at for CCW. If a small pistol is what you need, go for it. But if you can and are willing to use something bigger, I think you would be better off doing so.
