There is a best defensive weapon, but there is no perfect defensive weapon. Huge difference Sfury. A pistol is more versatile then a scattergun will ever be in a home defensive situation, meaning it can be used in more situations that will be seen in a home invasion. That makes it the best, well second best weapon. The best weapon is your brain, and being able to make an advantage of your situation. If a shotgun could be used for face to face confrontations, as well as across the room shooting, or tight manuevering in a hallway, then I could see your point of view, but lets face it, its not, and never will be. A pistol will outperform in some of those situations, and match or beat a shotgun in the rest. Do your research on this, by professionals who train average joe to police swat, and they will dismiss a longer weapon then the handgun for inside the home. As for relying on technology, I said Im not a fan of lasers, however, a firearm is not a basic tool, and has many parts, and are known to failures, and breakage. You have to make a leap of faith at some point, otherwise you best be a master of martial arts, or have Harry Potters wand.
I am going to say though, that seeing what IDPA uses for shooting, and in trying to simulate shooting behind obstacles, etc, like you might see in a home, or apartment, they use handguns. And part of the doctrine of IDPA was to allow as realistic practicing of self defense as possible. Think if the scattergun was so much more superior, they would be competing head to head with pistols, but they dont. It looked cool in Zombieland, but thats about as far as it goes.