Most of the major components are made by a handful of manufacturers. About the only thing that seperates any of the brand name guns is quality control. Most any of the off the shelf products from the bigger names are going to be comparable.
You don't say what your intended use might be, but if the higher end of accuracy is what you're after, you might want to read The Heavy-Barreled AR-15 Varmint / Target Rifle wherein the results of testing Bushmaster, ArmaLite, Doublestar, Rock River Arms, and DPMS varmint guns are related.
For less acute usage, I can tell you that my Colts (6520 and 6920) will punch holes in paper at least as well as I can point'em, and I suspect most of the other major marks are also equal to that task.
BTW, unless you're licensed for full auto, an M-16 is not what you're after.
Just to add another to your mix to consider - S&W recently brought out an evil black rifle (they call it the M&P), and it seems to be capable of sub MOA groups at 100 & 200 yards.
Compass Lake and White Oak are excellent choices for accuracy as well, you'll find a lot of competitors using both.
I recommend the Rock River because it comes with a very good trigger, a very good barrel with a tight enough twist to handle even the 80 grain VLD's. Any commercially available match ammo should do well in the 1:8 twist.
Colt offers a 1:7 twist which can handle even heavier pills, but it takes handloading to use them since I know of zero comercial loadings for the very heavy 224 cal bullets.