Which of these guns should I choose for Home Defense (apartment)?

Hey all I am 21 and looking to purchase my first gun. My wife and I are having a baby this summer and I figure it is time to get serious about home defense. I have fired a few shotguns and rifles but have never had my own. We live in a 2 story apartment with both bedrooms upstairs and living area down stairs. Neighbors on both sides so over penetration is a concern. I am torn between a shotgun and handgun. I am looking at either a Remington 870 (not a tactical as I would like to be able to duck hunt also) or possibly a .38 or .357 revolver, or a .45 semi auto. I would use bird shot if I choose the shotgun. With the pistols, is there some sort of ammo I can safely fire in an apartment if I had to. Although a shotgun is my first choice, I am worried I have no good place to conceal it in my bedroom. A pistol vault box would be much easier to hide. Also a pistol would be easier for my wife to handle in a stressful situation. Any advice on what to get would be great! Thanks