Unless you have a compelling reason not to (routinely hiking around aggressive bears, for example), I'd stick with 9mm. You want a proven hollow point round. My personal preference is Federal HST. Speer Gold dots are also good, as is Hornady critical defense. Stay away from novelty ammo. Ideally, find out what round your local law enforcement issues and use those. Thus, if a prosecutor asks why you chose a particular load, you can point out that it's what the cops use.
Glock is just about the simplest, most tested, most reliable semiautomatic pistol in the world. Also what most cops use, see above. There's a shitload of aftermarket support, holsters are widely available, and mags are cheap. I, personally, hate the way Glock grips feel in my hands, so I don't shoot Glock. But I can respect the reputation.
First generation Smith and Wesson m&p pistols had a really, really lousy trigger. Entire companies made thier names offering trigger solutions just for that gun. However, the m&p 2.0 has corrected that. It's a solid gun. The grip texture is extremely aggressive, like low grit sandpaper, but some people like that. The gun certainly won't slip out of your hands. However, the grip will wear holes in your shirts and abrade your skin until you develop a callus.
I don't, personally, feel comfortable with modern polymer framed SIG pistols. The p320, in particular *may* be capable of firing without user input, in the holster. This is a bad thing. Lawsuits are ongoing; many believe that the reports of spontaneous discharge are due to people handling the weapon unsafely and trying to cover thier negligence. However, this is not the first time SIG has released a firearm with glaring action failures; the early iterations of the Cross rifle sometimes discharged when the bolt was closed. Review the literature available, make up your mind, but they scare me. Also, the bore axis is high compared to many other options, so you'll have more muzzle flip.
FN 509 pistols have a solid reputation, from what I've heard. The one I rented didn't feel awesome in my hands, but it was better than the Glock. YMMV.
Beretta's 92 / M9 is a solid pistol. It's heavy, because it's metal framed, but very reliable. Many of us learned to hate the things by using military issued pieces that were abused to the point of materials failure. However, I've heard nothing but positive reviews of new, factory Berettas. I'm, personally, not a fan of the inconsistency of double/single pistols. Your first shot has to cock the hammer using the trigger, and subsequent shots are much lighter. With adequate training, it's not an issue. I'm just not a fan.
1911s are, IMO, too finnicky to make good carry guns. They are very sensitive to magazine problems and ammo problems. They also suffer from the same weight issue as the Beretta, having a steel frame. Also, single stack 1911s are very limited in magazine capacity, having 7 to 10 rounds per mag, compared to 15 to 20 in a double stack magazine. Many 1911s don't include a frame rail for light mounting. Finally, cheap 1911s tend to be low quality (Kimber, SIG, Rock Island), and expensive 1911s tend to be stunningly expensive. They do, however, have a *superb* trigger design, and are easy to shoot quickly and accurately.
The alternative if you really love the trigger on the 1911 is a competition-oriented design called a 2011. This is essentially a double stack version of the 1911. They start expensive at the relatively low end ($2k or so), and become ridiculously expensive at the high end (oh, about 8k). Keep in mind that your carry gun may someday end up in a police evidence locker. If you're carrying a 2011, you will cry.
Okay, (I hear you wonder) if everything sucks, what do you carry?
Personally, my carry piece of choice is the CZ P10C from the Czech republic. Internally, it's so similar to a Glock that I'm astonished there haven't been patent infringement accusations. Decent trigger, not fantastic, but reliable. Externally, the grip is a very organic hand shape, which makes it super easy to shoot. At 15 rounds capacity, it has enough ammo for the job without having a ridiculously long grip. And at $550 or so, if I gotta replace it, no big deal. IMO, it's the best option available right now. YMMV.
Once you've chosen a pistol, there are some (somewhat expensive) accessories I recommend. I'm a tremendous proponent of red dot sights. At this point, I don't think I own a single firearm without an electronic optic. They just make it *so* much easier to put rounds on target, quickly and accurately, in poor light, compared to irons. Especially with a weapon like a handgun which, by necessity, has a short sight radius.
Most of the above weapons have an option to get the slide from the factory milled for a red dot. Do that.
Vortex red dot sights are functional, but without automatic brightness adjustment, I don't feel they're suitable for concealed carry.
Holosun has a huge following, and they do a good job of cranking out relatively inexpensive sights that are sturdy and have the necessary features. Of interest, most of thier sights have a little solar cell that supplements the battery. Additionally, they offer a circle-dot reticle that is easier to pick up and shoot quickly than a simple dot. I, personally, am not a fan of the automatic brightness adjustment. I feel that it doesn't respond quickly enough to changes in ambient light. I'm also not big on using Chinese optics. But they're adequate, and you can get one for $300 or so.
Aimpoint has a fantastic reputation. However, thier pistol sights do not offer auto brightness adjustment, which I feel is a requirement for concealed carry.
I hear good things about pistol dots from primary arms and swampfox, but I haven't used them and can't comment.
My personal preference is the Trijicon RMR, with no buttons on the sides, and a 6.5 MOA dot. The battery lasts for about 3 years under normal use. I replace mine annually to be safe. The sight is rugged as hell, the brightness adjustment is fast enough that you don't notice it, it's easy to zero, and it just *works.* The issue is that they run about $500. I own about eight of them.
Finally, I believe that a defensive gun should have a light. You have a legal responsibility to *know* what you're shooting at, in any light condition.
Stay away from Olight; they have a tendency to either fail under recoil or...explode. IMO, there are two serious options for pistol lights: Surefire and Streamlight.
Surefire has a strong reputation for durability and quality. However, I feel that most of thier lights are a) too big for concealed carry and b) overpriced.
The streamlight TLR-7 is what I use on my carry gun. It nestles under the barrel more tightly than a lot of other options, making it easier to design a holster that protects the trigger. The user interface is quick and intuitive.
