i would go with LMT, Daniel Defense, Noveske, and (my favorite) JP Enterprises.
Armalite are good, Colts have the Colt name, Ruger's AR has a carrier tilt problem (i am usually a ruger fan, especially on SA revolvers), i have had problems with poor machining on parts with Rock River.
the top two companies in my opinion that make the best ARs are Noveske and JP rifles.
here is a picture of a JP upper (tactical upper not their standard competition uppers) on a Mega Machine Shop billet lower
(i highly recommend you build your own from parts... you can build a really high end gun, much better than Colt, DPMS, RRA, Armalite... ect...)
i started to build it trying to save money but have dropped way more than a standard rifle costs. right now, w/o optics it is costing more than a noveske...
i wouldn't change a thing, i LOVE my rifle and especially the way it looks...
build one to your liking, a webstore called
RAINIER ARMS is a good place to look if you want to build a custom gun on a billet lower.
all of their stuff is top of the line!
http://www.rainierarms.com/
no, i dont work for them but i was able to find stuff there that i haven't been able to find anywhere else
MIL SPEC
if you want MIL SPEC, just make sure the one you are looking at is MIL SPEC, mine is not Mil Spec, but it is by far not a POS.
MIL SPEC means MIL SPEC, not "BEST", but it is built to a specific standard. some stuff that isnt Mil Spec is bad, other stuff is better. MIL SPEC is kind of like piece of mind i think for most consumers...
personally, i could care less
if you are not looking to build, i would look at the companies i mentioned here (NOVESKE, JP, and (oh yeah, forgot) Knight Armament (which is the company that Stoner went to after he left Armalite, but these things cost so much that it will make your head spin and are perhaps the premier AR company); second choice after those are Daniel Defense, Patriot Arms (good stuff), LMT, Colt (starting to make better guns, quality control is getting better); third choices are Armalite, then RRA, Spikes Tactical (something about them i like and something about them i dont and i cant place it, just a gut feeling), Yankee Hill (a good company too), DPMS, Stag Arms, CMMG, S&W, and Bushmaster.
honestly though, all AR companies are pretty good, just avoid Olympic!!!!
check out this link to AR15.com's AR manufacture list/forum:
http://www.ar15.com/forums/board.html?b=2
GOOD LUCK!
any questoins just message me, i dont check in here often but i have the same handle on ARFCOM, GRM, RUGERFORUM (both), and a few others...
always up to giving advice and what i know....
most my time is on ARFCOM and Rugerforum.
anyway, my 2 cents, here is my pic of my JP upper (i highly recommend them, expensive but worth the price)
JP's website...
http://www.jprifles.com/