A couple of quick thoughts for those of you that have posted the questions:
I recommended hollow-points as opposed to FMJ not for their stopping power, but for the lesser chance of over-penetration. Yes, they can still get fouled by heavy clothing, at which point they're "reduced" to the impact of a regular round-nose bullet.
I still don't think that a .380 is going to offer enough take-down compared to the larger rounds, but given the stated goal here of choosing a caliber for use in an apartment, the Browning 9MM and Colt 1911 .45 are overkill, too much firepower and too complicated to operate. A .38 Special will give -almost- the same ballistics as a 9MM or .357 round, just not as potent. Plus, the recoil is quite a bit more manageable. Once you've increased your confidence and abilities through practice & lots of target shooting, you may want to consider stepping 'up' to a semi-auto. But not right away.
For someone with little experience with firearms (as is the case here), I'd lean towards one of the double-action 6 shot revolvers in either .38 Special or .357 Mag using .38 Special rounds. Something like a Ruger SP101, Colt Detective Special, or one of the many S&W versions. Once loaded, you just aim & pull the trigger - no safeties, slides to manipulate, etc. In the event of a bad round all you have to do is pull the trigger again.
If I only had one firearm to depend on I'd choose a shotgun, but there's way too much emphasis here on the idea that accuracy isn't important, or just "point in the general direction and shoot" mentality. At 20 feet, the spread on a 00 buckshot load is only going to be about 3-4 inches. Before you assume that you're going to clear the hallway with one shot, take a few targets out to the range and test yourself first.
edited for clarification