I'm planning on buying a SASS, but can't decide which one to purchase. Does anybody have either the Armalite or DPMS version, and if so, how do they perform? Quality? I noticed that the DPMS version has an 18" barrel as compared to the Armalite's 20" barrel. Does the shorter barrel give a noticeable difference at longer distances? I'd like to shoot 800M or beyond. I've always used a bolt gun, so any help will be greatly appreciated. Thanks!