1) The things said about a handgun are true. Mix tired muscles with a rush of adrenaline, and it's going to be tough to pull a 3-foot, 6lb shotgun into action leaning in the corner compared to a <2lb handgun off the night stand. For me that is more important because I can see the tile behind the front door from my pillow, so I wouldn't have much time to prepare for something barging through my door.
2) A shotgun is definitely not as easy to wield in tight quarters. Imagine walking past an open door and the BG is waiting in that doorway. He could easily grab the side of the barrel and push it away. A handgun, however, can be tucked into the chest with the elbows out to drastically decrease the chances of a BG getting his hands on it.
3) Realistically, a shotgun is much better for static defense. If you plan on crouching next to / behind the bed with the muzzle aimed at your doorway while your wife / partner calls the cops, nothing can beat the shotgun for close range. However, if movement is required (typically either if there are children / friends / relatives that need to be retreived, or if the homeowner is being unnecessarily brave), then the handgun is better. As stated, the off hand could be used to hold a phone or flashlight, to open a door, to hold on to said loved one, or even to fend off an attack while still maintaining use of the firing hand.
4) Avoiding over-penetration is definitely a priority. People often overlook the legal ramifications of even a justified self-defense shooting (not so much in Castle Doctrine states, though), and endangering or actually harming an innocent, especially through walls, will give tons of power to an aggressive prosecutor. Imagine that lawyer saying something like "oh, so you wildly shot at everything that moved, with no care if you killed some innocent child sleeping in his bed?"
5) However, DO NOT count on birdshot to incapacitate a threat!!! It will leave a nasty-but-very-shallow flesh wound that will hurt, but will still give the attacker minutes, if not hours, of full functionality. A neck- or face-shot would do the trick quite well (eyes being put out, mostly), however. I am not saying don't use birdshot--in your case I'd almost say it's the only responsible option--I am just saying don't expect the BG to instantly fall to the ground, and DO expect to fire multiple shots!!
6) That brings me to my next point: Anyone who will enter your home while it is occupied is either prepared to deal with your presence, or is crazy enough to not recognize that anyone is home, making him a very big threat anyways
. In either of those cases, the key point is that the intruder is not affraid
. Of course, it's possible that they might be scared away by racking the slide, but that is only a chance. What we do know
for sure is that by racking the slide, as stated above, it would guarantee
that the intruder knows your location (at least roughly) and that you are armed. If you are scared of keeping a shell chambered all the time, just chamber a round when you go to bed. The only sound you should be making is flipping the safety off.
7) To the OP: Since you can't buy a handgun anyways, don't worry about it. A shotgun (with birdshot) will be safer for your situation and much easier to use effectively. On that note, I'd also go with a 20g for less noise and more controllability without sacrificing much in the way of power. No type of rifle should be a consideration. Even with good training, the chances of a miss are much higher than those of a hit, unless you are ready for him as he enters a doorway. And even then, if he's a foot shorter than you expected, or if he's not centered in the doorway, you could still very well not make a clean hit (shoulder or arm, for example) or even miss altogether, endangering anyone in the path of the bullet through several walls.
I live in an apartment also, but filled cinderblock walls separate all the units, heh. Good luck with your purchase! Go with the 20g shotty