They will all do MOA or better if you know how to shoot that well. The bull barreled DPMS will probably be slightly more accurate since it has a stainelss steel barrel... but it will weigh a whole hell of a lot more. That would be an OK choice if you want a gun to shoot off the bench with all day, but if you are talking about a rifle for any kind of practical use, you may find it too heavy. If you want a heavy bull barreled bench gun, RRA and Armalite make rifles with that kind of barrel too. If you want a nice 20" light profile barrel, like a battle rifle, DPMS doesn't have anything in that category while the standard RRA and Armalite do. They all have light profile barrels in 16" length though, if you want a flamethrower that will simultaneously blind you and give away your position in low light. The Armalite takes Armalite mags. The RRA uses FAL mags. The DPMS uses KAC/Magpul/c-products mags, which gives you better selection and price (FAL mags aren't as cheap as they once were).
Your original question was about accuracy, though. There is really not enough difference in accuracy between any of those to matter for any kind of practical application. What are you going to be doing with it, anyway? A deer won't care if one rifle shoots a 1/8" tighter group at 100 yards. Nor will a human. Heck, people online who you show your amazing sub-MOA groups you shot with the rifle in a table vise pulling the trigger with a string (which you would likely have to do to detect any inherent accuracy difference between these different makes) probably won't care, either.
The real question is what can you do with that rifle, or any rifle, from unsupported field positions?
Sadly that dirty Rhodie in the above pic could probably outshoot most .308 AR owners with that old beat-up R1A1 from field positions.
I would also prefer a FAL, or better yet, an M-14, to any of those direct impingement AR designs, but that's with my particular uses in mind and my own preferences. The most important thing is to buy a rifle, any rifle, and become proficient in it's use.