Personally, I prefer a 12 gauge repeating shotgun (pump or semi auto) for dedicated home defense. There isn't a handgun in the world that is even near it. I also don't like pistol grip shotguns. They look cool and they are easier to maneuver but they are a cast iron #$%^& to shoot and aren't ever going to get high marks for accuracy. Besides, there's no telling when somebody is just gonna need a good old fashion butt stroke.
If you insist on getting a handgun, this is what I suggest.
Find a midbore (9mm, .38 Special, .357) semi auto or revolver that fits your hand well and learn to shoot it. Just making it go BANG!! isn't going to cut it. Handguns aren't as easy to shoot accurately as most folks think and big bores (.40-10mm and up) aren't as forgiving recoil wise as you'd think. It's too easy to develop bad recoil management habits like flinching or milking the trigger when you try to learn on one of them. Been there, done that. It took me years and a couple thousand rounds downrange to get over the bad habits I developed.
Take some basic instruction in handgun safety in particular and firearms safety in general. After all, you gotta learn how to be safe with it, so there's no need to start out forming bad habits that will need to be broken.
While you're at it, take a basic handgun course, too. Once you've been taught the basics, buy a case of practice ammo (that's 1,000 rounds give or take a couple hundred) and PRACTICE what you've just been taught. No marathon sessions are needed, just 100 to 200 rounds a week- if you make the concerted effort to make every round count instead of getting all giggly because you are actually shooting a gun.
Start shooting 2 handed with the targets CLOSE- like 12-15 FEET. When you can consistently shoot a group that you can cover with the bottom of a Coke can, move it back 3 feet. If your groups start opening up, move it back in and start it over. Keep doing that until you are at least as far as the longest possible shot in your house. I suggest doing the same thing 1 handed and even off hand only as well. There's no telling when you may be in a compromising situation (like holding a flashlight or your kid in one hand and the gun in the other) and need to use only 1 hand or even your off hand. Things usually don't turn out like we plan or we want them to, so it's best to be at least slightly prepared for that eventuality.