god forbid this would ever happen, but since you asked...well, if it's an actual breakin, assuming i'm in bed, then i'd reach for the mossberg 590. it's got a flashlight on it.
daylight hours - even more unlikely - sling the ar and grab the 1911. why? because if it's daylight, i'd have a chance to talk the intruder / assailant down while five-oh arrives, and it's easier to mark a target with a pistol for longer periods of time than with a rifle. the ar would just be there to, uh, bolster my side of the argument.
but remember kids, you're asking for trouble if you shoot anyone outside your house. most likely you'll do time. a travesty of justice, if you ask me. but if he's inside your house, no problem, pull that trigger. there's no castle more sacred than one's home after all. i got this straight from a criminal defense lawyer.
and lastly, of course, if all hell breaks loose and the enemy has breached the hull, then simply activate the self-destruct sequence and abandon ship...