Some mentioned tactics over weapon choice. Eschewing artillery, air and armor support for just a moment we come to the root of this discussion - the single soldier and his armament, which leads, by natural correlation, to his employment. For insurgents and those who spend more time hiding than shooting, any gun can do. For the individual soldier in an organized army, much more is possible.
Let's face it, there is plenty to be said for infantry with much maiming ammo on hand (remember, we now employ the philosophy of maim 'em, not kill 'em), multi-use, portable weaponry and mobile, squads tied together with good on-site comm gear.
This is the face of the modern fighting man. The lone rifleman with his well placed shot has value, but as an adjunct to the total picture.
(I thought it interesting to note that even in WWI, 7000 rounds per enemy killed was NOTABLE. Apparently, someone was missing out on how "great" those '03's were.)