Battlerifle=.30 cal semi or bolt action
Assault rifle= smaller round for more controlled recoil, optimised for 400 metres or less fighting, also has the significant advantage of much more rounds per pound.
Being able to carry 3 times the cartridges as the M14 as well as a controllable full auto made the M16 the better choice.
The israeli hit teams use local capture AK's because they sound like the locals weapons and don't invite the reaction a M16 would.
My choice of a battlerifle instead of an assualt weapon is because of the terrain
and a very strict 5 round per mag limit for most rifles. There are few exceptions but one of them is the 10 rounder allowed for the Enfield which is my personal choice. Another is a Garand is allowed 8.
I would love a semi M14 clone called the Norinco M 305. They are in most people I know who have both a better gun than the Springfield and only cost 400$ to the Springfields 1000+$.
This is a very basic M305 build like I would do.
They make a great 600 metres or less sniper rifle or hunting rifle.
Sage style builds are getting popular but I find them fugly. I do love a nice Socom build all pimped out with a cool Trijicon or other nice site it's still cheaper than the bare cheapest Springfield.
Another rifle I want is a nice SKS with bayonet and a pallet of 7.62/39.