While at Suwon AB,Korea in 69-70 our CSC building had a huge room full of M-14's with boxes and boxes of ammo. Whle working in the armory I occasionlly would take one out to the range for fun...definately more bang for the buck but harder to control...three shots and you've climbed off sight picture. A mixture of tools (weapons) to get the job done seems desireable but logistically becomes harder to support. Personally, I think an AR-10 would be a great all purpose weapon, espcially if they sported it into M-4 configuration for house to house duty.
The Russians actually have a very interesting take for house clearing - a short-barrel AK shotgun in full-auto.