Shootall.
Maybe I am not the one to talk on this.
When I think I need a gun, i carry one based on the threat level I think I will encounter. Clearly walking around in the suburbs on a sunny saturday is a different threat level than that same walk at night or in the inner city or on a construction site. going to the mall and parking right in front on a semi busy day is different than parking at night far from an exit at christmas time when the mall is packed and people are not paying attention lots of cash is around and preditors are looking for the weak ones in the heard to attack.
What I carry I have practiced with and am confidant I can hit what I need to.
I practice stressing my self out with timers, excersize, and hoilding my breath. Some times all three. holding my breath I will do 10 push ups and then still holding my breath try to get 6 rounds at 21 feet into a 4" circle. thinking if I can hit that I can hit the neck on someone. There are a lot of blood vessels, and nerves in the neck that may give me the best chance to stop the attack as well as most vests do not cover the area.
The times I was worried and had a few guys tell me I was not going to testfy against their friend I was packing my P226 with as many rounds as it would hold and a few more in spare mags. Lucky for me I was met with two guys with bats rather than guns in front of my apartment on my way home and I moved out the next week. To Richmond actually from Va Beach.
Other than that I have been very lucky and depending on clothing and I will carry what i can.
Now That i live in N. CA heavier cloths are not a neon sign of look at me that they were in the desert in S. Ca. where Khaki pants and a Polo shirt are the business atire adding a blazer, jacket, or vest would not allow me to blend in.
With the 45 Vs. the 22 story i am trying to point out that shot placment is the key and that 7 rounds of the magic 45 acp may not work if you hit parts that do not end a fight through blood loss, Blood pressure loss, or a nervious system loss. As Capstick used to say shoot the biggest gun you can. A round of 375 H&H in the right place is better than a 470NE in the wrong place and a Buffalo will run over you faster on three legs then four.
Granted if you are good with a 45 it will be better as the wider heavier bullets are what cause blood loss by making a lot of damage and large drain holes, blood pressure loss by giving you a larger wider bullet that has a better chance of hitting a major blood vessel and de-priming the pump, and the same with the nervoius system it has the mass to make it through bone and carry that energy through to spine, or brain.
Would I hand someone who has not shot a gun my mouse gun and say this will protect you. NO! if it was the right fit for the situation and they were willing to practice with the gun, learn to shoot under stress and on the move. Then yes I would get them to carry the largest gun they could and not make them a target for someone who sees it and tries to take the gun from them.
As far as calibers for handguns go for personal protection. All the auto loader duty calibers are the same, the mouse rounds are the same, and the 2" revolver rounds are the same. You need to ballance threat level (how likely am I to be attacked and by how many), ammo carried ( would it be better to carry 9 rounds of 32/ 9mm or 7 rounds of 380/ 45acp), skill with the gun ( can I make effective hits to stop a fight in less than 3 seconds), and size of the gun ( is the gun too small/ large to be able to get it into action- can it be seen making me a target- Does it fit in my hand).
Ballancing out all of these is what will make a carry gun for you. In your case a Bradly Fighting vehicle sounds about right.