When it comes to facing the many choices available in terms of home defense, decisions can be difficult. What follows is only my opinion, agree or disagree, I am just putting this out there because I was asked.
Handgun or Long Gun
I would recommend the long gun in almost every home defense situation. With the long gun you have three point contact for better control, greater accuracy, and the ability to reach farther if necessary. I have heard the argument about handguns making it easier to use the other hand to hit light switches, etc. You get eliminate that issue with a flashlight attachment on your home defense long gun.
Shotgun or AR 15?
Well, that is a bit tougher to say. Either one is a great choice. I’m not being cagey, not trying to play both sides. I really like them both.
ARs have great capacity, accuracy, low recoil, and are easy to operate. With a little practice you can become a very good shot. There are also a ton of accessories you can pick up to completely customize your AR-15 into something that meets your specific needs for home defense. The most common round used by the AR-15 is the 223/5.56, which has a tendency to tumble when passing through a body. What this means in terms of home defense is the round is less likely to punch through the bad guy and the wall behind him. This is a good thing.
A 12 gauge shotgun has lower capacity, much higher recoil, but it also punches the bad guy a lot harder. Having said that, I would add that the shotgun pictured at the top of this post holds 8 shells with nine 00 buck pellets each, making 72 projectiles, which is higher capacity than an AR with a standard capacity magazine (30 rounds). Shotguns are also versatile outside of home defense. With a 12 gauge and the right load, you can hunt anything from varmints and birds to deer and elk. You can get shells loaded with anything from tiny ball bearings to a single .72 caliber projectile.
The best answer is simple, but you have been told before. The correct answer is to choose the gun that you can handle, can afford, and will be willing and able to train with. If you are smaller framed, maybe the AR is the better option. If you can handle a bit more recoil, shotguns are awesome. It really is an individual decision. But whatever you decide, I cannot stress enough that training is the most important factor.