Well my vote goes to Bushmaster, why you ask? This is why:
1. About a year ago, when I was doing a lot of research on AR-15s trying to decide which one to buy, the Bushmaster came highly reccomended from just about every website and person I talked to. The only place I see Bushmaster get a mediocer rating is here. There are a few reasons why I feel this may happen, but I don't feel like elaborating, as it is just my own speculation.
2. Out of the big manufactures, from what I have read, the Bushmaster is the most in-spec rifle, even more than the civilian Colts.
3. Every colt that I've ever handled, from military M-16s and M4s, to civilian AR-15 rifles have been P.O.Ss. At the time I was looking into this, I had enough money to afford a colt if I wanted one, so price wouldn't have been a factor.
4.Quality, I know when I buy a Bushmaster, I'm getting a quality firearm.
5. Price to value ratio. Why spend more money on an Armalite, or Colt, when the Bushmaster gets it done as good if not better?
I have had my Bushmaster M4-A3 for about a year now. I have shot probably about 1,200 to 1,500 rounds through it without any failure of any kind. I know that isn't a lot of rounds, but it's proven itself to me as a good reliable rifle. I wish I had the money to do my own testing on the Various different brands. I usually only shoot 200-300 rounds per outing and then I clean it. I don't know how well it will hold up for a extended pieriod of shooting time without cleaning, but from what I can gather, it will go strong. My roomate has a Bushmaster M4A3 (we bought them the same day) and over one weekend, he shot 3,000 rounds with no cleaning or lubing what so ever, with a various assortment of ammo (Him and a buddy where cleaning out small sports stores of all they're .223 and 5.56 so they got a whole variety of loads.) and it all shot beautifully. He said he dropped it straight in the dirt on accident on the ejection side, but just rubbed the dirt off and kept shooting with no problems. He said when he finally cleaned it at the end of the weekend, there was a bunch of sand and grit in the carrier, but that it didn't mess with the rifle one bit. I am extremely happy with my purchase and will reccomend Bushmaster to anyone, and I push them Hard at work, yes even over the more expensive Colts. The only other one I might have gotton would have been RRA. What turned me off about they're rifles was not having a chrome lined barrel. I think they may have changed that though, and if not, it's an option, I just liked the fact that it came with one. The RRA does come with a 2 stage trigger though, which is nice, but I think I would rather have a regular trigger in my rifle for a combat gun, and the 2 stage in my target guns, That's just me thought. Your milage may Vary. I hope this helps.