Quick question for small arms buffs

[Marcello]

Ditto for the 10 hex LMG vs. the 12 hex.

It is usually an issue of weight and ammo compatibility with rifles. Not everyone has gone down that route, PKM are pretty popular AFAIK.
Contest must be also kept in mind. When the Lee-Enfield was introduced MMGs were a newfangled toy,as late as 1914 a british infantry battalion would have IIRC two of them (and it was considered to be a generous allotment),and LMGs were only on the drawing board.
So a rifle with good range was necessary, because the only alternative was artillery. On the other hand a WW2 german squad could count on its MG42 to reach beyond individual weapons and options have only increased since then (grenade launchers, more responsive fire support...).