I think the answer is to have two copies of at least one handgun, train and compete with them, and have a good attitude. Cirillo talked about what makes a good gun fighter in
Guns, Bullets and Gunfights. Most of the discussion was about the man's general attitude, training, competition, and overall moral philosophy. Cirillo did mention that when the fight occurs (paraphrasing) that you'll want the biggest gun with the most ammunition possible.
My thought is to divide the gun's capacity by four and drop fractions. This is how many bad guys I can theoretically handle without reloading. A J-Frame yields one, 1911's are good for two, and a Glock 19 is good for four. This is likely not realistic at all, but it's my best wild guess based upon training. My most pessimistic estimate is 8-10 rounds per bad guy (resulting in 1, 1, and 2). I could hit the "gun fight lottery" and get 16 terrorist scumbags with a G19, but the odds of that happening are only very high on a Hollywood set.
Confidence is a key ingredient. Michael de Bethencourt is confident with two snubbies for everyday carry. If a person does not have confidence with the gun, then I think he or she should consider other options. However, there will be exceptions and merely having a gun is the best that person can do in the situation.
I think a five shot J-Frame is likely sufficient for many types of encounters. It is not good for all encounters. Ed Lovette covers the snubbie's strengths and weaknesses in
The Snubby Revolver: The EQC, Backup, and Concealed Carry Standard. I think there are better choices today because of improved technology and design. However, all it may take is one shot to stop the attack. Several mass murders were stopped early because a determined person with a gun resisted. Only in a few cases did the murderer attempt to engage the good guy; many times they fled, surrendered or committed suicide.
I have my carry battery that includes a J-Frame and small pocket autos. I try to keep them out of the primary role, but sometimes wardrobe requires pocket carry. I'd rather have a J-Frame and five extra rounds over nothing. I'll just do my best if a fight occurs.
One compromise that I am willing to make is lower capacity for a larger caliber. This is not to say I won't carry a Glock 19; I do carry one frequently. I prefer 200+ grain bullets moving at 800-900 FPS at 25 yards over the 9x19mm bullet traveling at 1150 FPS (muzzle). My second choice is 357 Magnum or some 9mm variant with very high velocity. But, I prefer the larger calibers. As a result, I'm willing to trade some capacity for the bullet. I do not mind the larger frame either; concealment is not difficult, but it does require some preparation. I do think the Glock mid-frames (and similar guns such as the M&P 45 Compact) offer the best balance between capacity, sight radius and concealment. If a person has no idea what to get, I usually recommend a Glock 19 because of these attributes. If they decide to sell the gun because they dislike it for some reason, they'll get most of their money back.