I believe there are seven criteria to help you through the decision process of choosing a CCW:
(1) The gun has to be with you when you need it. When do you need it? When you don't expect to need it (if you expected trouble, you would be armed with a rifle). A gun that is too much trouble to carry won't be with you when you need it.
(2) The gun has to be quick into action. (this drives the loaded condition of the gun and how you carry it)
(3) The gun has to be powerful enough to get the job done (your presentation of the gun may not deter the adversary. you may really have to shoot, and you want it to be powerful enough to cease hostilities with one well placed shot)
(4) Reliable in your hands (must always go bang)
(5) Accurate in your hands (hit what you aim at)
(6) Controllable in your hands (fast and accurate follow-up shots)
(7) the gun does you no harm (eg no magnaporting -- which depending on the presentation of the firearm could put hot gasses into your eyes)

With all that said, my choices are three: A Colt Ltwt Commander, a Walther PPS, or a Smith J-frame revolver.