The Best AR made is the Les Baer. Made precisely to the original prints, parts hand fitted, will out shoot any AR made by anyone else. Absolute quality. Deployed w/ snipers in Sand World..shoot under 3" @ 500 yards !
Will shoot 1/2 MOA out of the box.
you really can't go wrong with any of the major brands. sure there are some that get more air-play than the others, much like Ford-vs-Chevy-vs-Mopar. most of it all comes down to who your favorite team is, and how much you want to spend.
just because one got the contract for whoever, does not necessarily mean it was a quality difference...as with any government contract, whether it be federal/state/city, it all comes down to $$$'s. yes they do have to pass a quality test to be qualify to be in the running for that contract.
some have had quality issues in the past, most do get fixed in production as soon as those issues are identified. and even the best can occasionally let some lemons through. and then there are some that seemingly are in it just for the $$$'s, buying parts from overseas, without alot of attention paid to detail or quality.
do you get what you pay for? for the most part. but it seems like everyday a new kid shows up on the block with cheaper prices. then again, there are the big names (usually custom manufaturers) such as Les Baer, Wilson Combat, Fulton Armory, Knight, JP, etc. that offer high end products with $$$ signs to match.