1. Handgun. While houseclearing is to be avoided whenever possible, sometimes it is not (e.g., gotta gather the wife and kids into the saferoom). Handguns are much better suited to clearing, as their short barrels allow for better manuverability in tight corners and hallways.
In addition, the handgun is an excellent companion to a long arm in terms of weapon retention. If a goblin grabs your shotgun, unless you are trained in long arm retention and disarming, don't bother wrestling him for it -- let him have it, draw your handgun and shoot him while he's trying to get the gun oriented on you. You can pick up your shotgun later after he's down.
This is the reason why "tactical" slings are generally not recommended for the lone home defender -- if a goblin grabs your long arm, he is then able to drag you around as well, since you are attached to the gun by your tactical sling. If you use a standard sling, the sling goes with the gun and you stay in place -- which allows you to draw a better bead on him with your handgun.
2. I would recommend the one that fits your hands and that you can shoot well. Read the following for selection of a CCW handgun (but ignore the stuff on carry if you don't carry outside the home) at
http://www.members.tripod.com/~jth8260/buy.html
HTH,
Justin
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Justin T. Huang, Esq.
late of Kennett Square, Pennsylvania