Probably the AR simply due to familiarity and ergonomics. If a guy was more familiar with the AK then the Krinkov or the AMD makes about as much sense in such a situation where accuracy at extended range would not be an issue. I would not opt for the MP5 simply due to the caliber. A short AK/AMD or AR is as easy to manipulate in close quarters and offers more power. The shotgun does not offer as much precision if it were needed, and holds fewer rounds. The AMD with the 75 round RPD drum mag is pretty intriguing the more I think about it.
"A Liberal is someone who doesn't care what you do, as long as it's mandatory". - Charles Krauthammer