I find it interesting that so many of these "CCW questions" threads focus on the the "shopping list" for carrying concealed. But it seems to me the the important question is, "What do I need to know and what skills do I need to be able to effectively defend myself in a violent encounter?"
Being able to most effectively make use of a gun for self defense involves more than just picking the right gun and holster.
 You will want to know and understand the legal issues -- when the use of lethal force would be legally justified, when it would not be, and how to tell the difference. You will want to understand how to handle the legal aftermath of a violent encounter and how to articulate why, in a particular situation, you decided to take whatever action you did.
 You will want to know about levels of alertness and mental preparedness to take action. You will want to understand how to assess situations and make difficult decisions quickly under stress. You will want to know about the various stress induced physiological and psychological effects that you might face during and after a violent encounter.
 You will want to develop good practical proficiency with your gun. That includes practical marksmanship, i. e., being able to deploy your gun and get good hits quickly at various distances. It also includes skills such as moving and shooting, use of cover and concealment, reloading quickly, clearing malfunctions, and moving safely with a loaded gun.
Is all this really necessary? That will be up to you to decide for yourself. It will depend on your personal view of what you need to be able to do to believe yourself to be competent. But --
- If we wind up in a violent confrontation, we can't know ahead of time what will happen and how it will happen. And thus we can't know ahead of time what we will need to be able to do to solve our problem.
- If we find ourselves in a violent confrontation, we will respond with whatever skills we have available at the time. If all you know how to do is stand there and shoot, that will probably be what you'll do. It might be good enough, or it might not be.
- The more we can do, and the better we can do it, the more likely we'll be to be able to respond appropriately and effectively. The more we can do, and the better we can do it, the luckier we'll be.
We tend to focus too much on the tool. We get in extensive discussions about which gun or which ammunition or which caliber is best. But I've come to believe that any gun of good quality that is reliable and accurate in a meaningful caliber will do IF -- you can manage it, you get good training and practice regularly. Conversely, no type of gun will make up for inadequate training and practice.
I'm a strong believer in good professional training for anyone who is considering owning, and especially carrying, a gun for protection. It's partially a matter of being able to skillfully use it under stress. It's also a matter of understanding one's personal responsibility and the applicable law. Jeff Cooper used to say: "It is long been a principle of ours that one is no more armed because he has possession of a firearm than he is a musician because he owns a piano. There is no point in having a gun if you are not capable of using it skillfully."
There is something to be said for choosing a popular brand or type of anything, be is a pistol (Glock, SIG, 1911, etc.) car (Camry, Honda Civic, etc.) or pretty much anything else. If something is popular, parts and service will tend to be more readily available.