my experieance, a long boring post.
If a person is in the law enforcement business then maybe a bigger caliber would be more appropriate. When I was much younger I only had mouse guns, .22 and .25. One incident I lived in a rural area and at 2 am someone was driving around my backyard, parking, waiting and driving parking and waiting again. I didn't know what was going on but I was young, single, poor, didn't have a phone so 911 was out (acutally I don't thing they had 911 then). Anyhoo after about an hour and a half of this I really started getting scared. I cracked open my door and fired a shot to the ground, not towards the car, not yet. Didn't matter, they were burning rubber.
Another time, same place, hubbys "friend" payed me a visit while he was away. He wasn't going to leave until . . . Diplomacy wasn't working and I remembered my little pistol. I made an excuse to go to my magazine rack where I kept it, I didn't say "don't hurt me or I'll get my gun". I just went and got it. Once I had it I felt all better. I wasn't scared or shaking cause I knew the cards were stacked in my favor now. He wasn't too concerned at first and started to approach me. I fired a shot into a beanbag chair. He decided to leave. Never had a problem with him again.
Another time I lived in a bad part of town and looked out my window to find someone lurking. I opened my window and waved my little .22 revolver. They ran away.
I got tired of being poor and went to college and got my degree in medical technology. I carried my little revolver with me in my car, it was the only legal way to do that back then. Eventually my car was broken into and my precious revolver stolen. The car was in a garage with security guards. I have reason to believe they are the ones that stole my gun but I won't get into that now. I didn't leave a gun in my car after that. I kept my little one in my purse. Having that gun stolen made my physically ill. I kept seeing the image of some elderly couple being the victim of a crime with my gun. The thought haunted me for a long time, still does when I think about it. Parking garages are very bad places for safty. I now have started putting my glock in my glove compartment, only because where I park now is much more in the open and there are cameras. I keep the little one in my purse. Nobody knows I have either one. I have to drive through a bad neighborhood late at night and refuse to be an unarmed victim.
The point of this long diatriabe is that when I had that gun I was confident and did not respond with "shaking". Yes that was ignorance on my part but I believe my demeanor was a factor in the bg's decision to leave me alone. If I ever have to REALLY use my weapon it will be because I have exasted all other options and since I am familier with it and apparently can keep it together enough in these situations to place my bullet, I'm really not too worried about caliber.
A home invasion is another story. This is when I'm glad I have many firearm options. I have my 9mm and shotguns and rifles. I really don't think a person can survive 9 shots at close range to the head. If they do they will at least be wounded enough I can get away.
That being said, when I get the money I will make a purchase of a larger caliber, just because. Right now I am leaning towards a 10mm or .357. Whatever I decide will be a full size gun, I already have enough compacts. A .45 has not been ruled out. I shoot friends guns some and sooner or later one will stand out as the one I will purchase next.
But like I said, if I was in the law enforcement industry the rules change. You would be more likely to have to use your weapon on someone not as easily discouraged as what I might run into. I've never actually shot anyone and hope never to have to. If I do it will be there choice, not mine. I won't be a willing victim.