Over at gunnuts.net, Caleb Giddings started up a pretty decent firestorm with his post about if the shotgun is still a viable defensive firearm. To get in on the conversation and read Caleb's thoughts check it out here. While I am pretty much in agreement, I think that if you pose the question a little differently you can see the other side of the coin. If you change the question around so that it ask what can an AR-15 do that the shotgun cannot do I think you can catch a glimpse of why the shotgun is still a viable defensive option.
I have spent a few days thinking about this, and the only thing I am coming up with that an AR-15 can do and a shotgun can't is the AR-15 has more precision and practical range. It is pretty easy to hit moderate sized targets with an AR-15 out on the other side of 300 meters. Guys in the military do it all the time. But what use is that to the guy who is just running the gun in a home defense role?
Sure, an AR-15 is easier to shoot, but the shotgun is cheaper to shoot, cheaper to buy, and potentially cheaper to maintain. It is like I have said before, a shotgun is better than a handgun, and cheaper than either a handgun or rifle. In essence, the shotgun bridges the gap between handgun and rifle while being the most economical. Is it the "best"...of course not, but neither is anything else.