I own nearly 50 handguns. My answer really depends on the situation in which I would need the gun.
For concealed carry, I generally go with my Glock 23 (.40) and my Walther PPK/S (.380) as the back-up.
As far as a hands down favorite. I have to go with my Beretta 92FS. I've put close to 50,000 rounds through this gun, and of all the handguns I own, I am the most accurate and efficient with this gun. It just fits me the best. I have large hands and the bulk of the Beretta fits perfectly. I come out of my SERPA holster quickly and onto target in an instant. Tactical reloads are a breeze. I like the weight of the trigger after the first round is fired. The trigger is very light for rounds 2-16.
I know a lot of people aren't fans of the 9mm round, but it has better peneteration of soft tissue than a .40 or .45 ACP. Placement of your rounds is the crucial factor. Hits to center mass will be sufficient.
Mine is my XDM 9mm two tone. But a close second is my Smith and Wesson Governor.
Throw a couple .410 shells in it and shred anything. Just waiting for crimson trace to deliver a laser grip for it.
So far they seem ok. When you get the gun it comes with clips to use on the acp's. Two for holding six and two for holding two. They are kind of difficult to use. Apparently there is a tool that makes it much easier.
I mostly use it with .410 shells. They are fun.
Went out to the range today. With 410 shells it seems to perform the best. I shot with 6 shot today.
At 50ft the pattern was very wide. Only showing 9 or 10 pellet holes on a 8 inch target.
The closer you get the more the group tightens up. Going to try 4 shot and 00 buck next.
As for the 45acp mine always shoots low and to the left. With out much of a pattern. Again the closer you are the better it gets. But the funny thing is with 45 long colts I can hardly get a pattern at all. High, low, left, right.
And they are too expensive to shoot a ton of them anyway. As for the moon clips only the one that holds 6 is a
pain. I find it is even harder to remove the empties. The double holder is fine. I just use them more.