I really like Rock River products, have a bunch of their parts, a couple of NM AR's by them, and am ordering through a FFL a Bullseye M1911.
However the 308 version of the AR is still a rather recent thing. The original design never went through the Government prototyping and development and testing that the M14, FN/FAL , and m16 went through. These sort of tests cost so much money that only a Government funded agency can really afford it.
So what does this mean, it means that firearms based on the M14, FN and M16 are going to be highly reliable out of the box in a world wide context. Assuming good manufacturing. Springfield Armory has been building M1a's since the 70's. Early M1a's had their problems, but Springfield Armory's rifle is a very mature platform and very reliable. I have worn out several barrels in competition, never had a problem. The platform is dead nuts reliable.
I have no doubt the AR-10 type platform will be very reliable in time, but I do not want to be the product tester.
As far as designs, the M1a is still my top choice for a 308 semiautomatic rifle. FN second.