A FNAR and an AR-10 are apples and oranges. If you want a .308 AR, buy an AR-10. If you are looking for a long range precision rifle, buy the FNAR. I've owned both.
I can clover leaf rounds at 300 yds with an FNAR and make 800 yd shots with it consistently. It is was designed to be as accurate as a bolt, but to able to deliver faster follow-up shots, which it does. It was not designed to be a self defense rifle, that's where the AR-10 comes in. A fully tricked out and properly equipped FNAR goes 14-15 lbs, again not an all day SD carry rifle.
JMO.