Within the full context of their conclusions, it's certainly a bit difficult to argue...
During a lot of these go-rounds of comparing one critter to another, I think of Beirut and the Marines who died there. Even if the "gate guards"' M-16s had been loaded, how effective could they have been against a truck? That is, while the truck would eventually have stopped from flat tires and a shot-up radiator, could it have been stopped before the explosion? I think not. (The possibility exists that a .223 fusillade through the sides or into the rear of the truck could have detonated the explosives well away from the building--to the detriment of the shooters.)
The comment about supported Infantry is well-taken. Under the described conditions, the .223 is quite adequate.
Overall, however, "purpose" must taken into account or the whole issue of "Which is better?" is pointless.
Art
