I'm looking for a new AR-15. I want to buy quality, and I don't want to build a rifle, so I've pretty much decided on a Colt. I know some people say they are over priced and what not, but I believe, to an extent, that you get what you pay for. The rifle is going to stay 99% stock, if not 100%. My question is, would you go with an SP6920, or a AR6721, and why? Thanks for the input.