Some guys shout that its the only gun you should buy for the money because its all mil spec parts. They worship at the all mighty alter of mil spec. The fact is most guys never put more than 3 or 400 rounds through whatever AR they buy. With that said a cheap palmetto ptac gun will serve their purposes. and IF they really did need the perceived and maybe not even real extra reliability of mil spec parts they are shooting enough to want certain things on their ar 15 that the 6920 does not have. The 6920 is a basic ar 15. I think something rock river is alot better value. for one you should be able to get a gun with a decent trigger and maybe a better stock check out the RRA operator 3. its probably going to be a more accurate gun too.
with all that said, another option is buying a cheap AR 15, shooting it and then you will learn what you want on a gun. everyone has things they want on their gun that is important to them
I have a 6920 and it is a very good AR, since the prices have come down, that makes it even better, the only thing I don't like is the trigger, its pretty rough.
It's a really bad time to be buying just about any complete rifles, unless you have zero interest in replacing anything, or learning how to build them.