While I agree that a majority of the time the mere presence of a gun will end an encounter before it even gets started, and the few times when shots have to be fired, usually only one or two rounds are used, I would like you to consider what happened to a deputy I once knew (I actually didn't know him personally but I knew who he was as we sometimes nodded hello to each other in the locker room).
He frequently worked the evening shift and because he knew first hand what crime was on the rise, he felt uncomfortable with his young wife being home alone & unarmed while he was patrolling the streets and so, he bought for her a Raven .25ACP pistol. His wife was a small woman less than 5 feet tall and weighing about 85 pounds which is why, I guess, they went for a small gun -- something that would fit her hand well without too much recoil.
One night she heard someone breaking into her home. She grabbed her gun, chambered a round, locked her bedroom door and called the police.
From what I understand, the police were at the house in under five minutes (especially since it involved the wife of a fellow deputy). When they got there, they found the intruder dead a few feet from the front door and they also found the woman dead in her bedroom.
Nobody knows what really happened because the two people involved were dead but from the physical evidence, the investigators were able to put together the following ...
The intrudor kicked in the bedroom door and the woman starting firing. We don't know the order of bullet placement but one shot missed, two landed in the chest, one in the stomach, one in the shoulder and one in the leg. When the woman stopped shooting (because her gun was empty), the intrudor strangled her and tried to make his way out of the house.
Interesting enough, it was the shot in the leg that caused his death since it hit a vein or something causing him to pass out from the drop in blood pressure and caused his heart to stop.
The gun quickly killed him (in five minutes or less) but it was not successful in stopping him.
This happened nearly two decades ago and it has always stuck in my mind. For this reason, I am of the opinion that a person should have the largest & most powerful gun that they are comfortable with and can shoot accurately.
That doesn't mean that I'm recommending .45's & .44's. If a woman (or man, for that matter) has small hands and is recoil sensative, then I would advise a fuller size .380 -- which would still be the size of a compact/sub-compact. A .380 in that size gun doesn't kick much more than a .22LR put produces much better stopping results especially in loaded with the proper bullet. With regard to revolvers, if a .38 special is too big or kicks too much, then I wouldn't go any lower than a .32H&R Magnum.
Biggest may not be best but bigger is definitely better. Most people will never have to use a gun in self defense but the one time that you may need to rely on a firearm to protect yourself, or a loved one, may you not be found lacking.
Share what you know, learn what you don't 
