'Couple o' thoughts...
Not to get into a home defense gun debate, but thought I'd give some points to consider. I used to want a .410 pump shotgun, thinking that with a .410 you don't have to worry about 'shooting through walls', whoever it's pointed at ain't gonna know the caliber, and a pump has an outstanding detering effect.
However, my former supervisor runs a gun training ranch for competitive pistol, concealed carry classes, home defense training, and even does SWAT-type close-combat training for US and international police forces. He's changed my views.
IF you have to have a shotgun, .20 gauge has a lot better selection of rounds for home defense than .410. .12 ga is too much power and too much recoil.
Pumps have a great detering effect, but deterence isn't the best approach. If someone is in your house, shoot to kill. (my words, not his).
Pistol calibers are great for home defense, but no-one is as good with a pistol as they think they are, so his suggestion for the perfect home defense gun is a pistol-caliber carbine (with a red-dot sight). A carbine offers more accuracy than a pistol and more precision than a shotgun. Also, pistol-caliber carbines are shorter than shotguns, so are a little more friendly indoors.
Personally, I'm looking to get a Hi Point carbine in 9mm. However, it's so ugly I'll probably have to get an ATI stock for it. Wish I could afford the Beretta...
Oh, and a shameless plug: I've got a Savage .22/.20 ga. (as described above) I'm looking to get rid of. I mail ordered it from a Sears catalog a million years ago, and it's still in excellent shape. If anyone is interested, pm me.