i recently had the privilege of attending a multi-day (night) low-light shooting course taught by respected trainers.
night one included a brief introduction to defensive house clearing, and night two was a taste of offensive house clearing ... in a privately-owned shoothouse.
most of the participants opted to run the shoot house with pistols (5.56 carbines weren't allowed due to safety reasons). i ran the shoothouse with a pistol as well as a 9mm CAR (Rock River Arms).
anyways, based on my limited experience, I agree with Jeff White that carbines can be somewhat cumbersome to manipulate, especially around corners.
HOWEVER ...
i think a carbine has some (perhaps debatable) advantages over a pistol for low light home defense.
these are just my unbaked thoughts and impressions based on limited experience, take them with a bucket of salt:
first off, the carbine absolutely
SHINES when it comes to the long shot versus a pistol. if you have to engage a target across a long room, it's
much easier to place two rounds in a nice neat little hole on target than it is with a pistol, as pistols are inherently more difficult to shoot. remember, under conditions of stress (even training stress) your combat accuracy typically degrades to 50% of your range accuracy. so, i now wonder if my wife is better off using a carbine instead of a pistol.
secondly, i found the illuminated red dot sight (aimpoint comp series) a real asset under low light conditions. more comfortable on a carbine than a pistol.
thirdly, manipulating light was
much easier on a carbine than a pistol. a carbine mounted white light manipulated by the support hand is MUCH easier to use under stress than using a pistol and a flashlight (where you are essentially shooting one-handed). i understand the technology is getting better with pistol lights (i.e., surefire x300) so perhaps this will change.
Just my $0.02.
p.s. you don't have to run position SUL with a carbine in a 12-man stack either.