Is going on at Surviving in Argentina AKA FerFal's blog. My thoughts, rehashed from previous posts and maybe slightly evolved are as follows. The shotgun has some real benefits which relate just loosely to the weapon itself.
A servicable defensive rifle such as an AK, AR or some sort of .308 can be a real trial on a modest budget. For some folks it would take a very long time to save up for or just not be affordable until their situation changes. Defensive shotguns in the form of Mossberg 500's and Remington 870's are cheap. You can get them gently used and perfectly servicable for under $200 in used gun racks and pawn shops until you run out of cash or closet space. Of course like anything you can spend as much as you want. Somebody out there makes a $3,000 high tech custom defensive shotgun (interestingly unless it's a semi auto I would go dollars to doughnuts it's an 870 with lots of bells and whistles). However an 18-20" barreled pump shotgun will do 90% of what it will do at 10% of the cost. Bison's 90/10 rule definitely applies here. My advise is not to church it up. Get a pump shotgun, a sling and something to hold extra shells and practice.
Also there are a lot of bird/ deer/ skeet guns out there which can be readily put into defensive service with an appropriate length barrel and some buckshot. $10 bucks in buckshot and $5 in slugs turns a dove gun into a house gun. Versatility is a strongpoint here. If you live in an oppressive area then shotguns have another plus. They are not specifically targeted by much in the way of anti gun legislation. They are umbiquitious and within their performance envelope an effective weapon.
If you can afford a good semi auto rifle then you should get one. It might be the way to go for a home defense long gun. However if your budget or inclination lean towards a shotgun that is fine too. Understand your chosen weapons strengths and weaknesses and train with it. It is generally more about the person behind the gun than the gun itself.