To answer the original question, if it's going on a Colt, I'd get the Colt, for the uniformity of it. If it's going on an aftermarket piece, I'd get one of the aftermarket pieces. but NOT Bushmaster.
Why? Because ALL the major aftermarket units are exactly the same; made by the same people in the same plant, on the same machines. Bushie gets considerably more for their unit than Rock River, or anyone else, and except for the emblem on the side it's the same damn thing.
Re the fancy ass piece that all the "Commandos" above keep pushing; why not wait until we see if the ban gets lifted. If it does, you can spend the bucks on a real collapsible then [:D] If it's renewed, then you still have a legal M4gery in appearence, w/o having spent a lot of dollars for a non collapsible piece that isn't even GI looking.
Just a traditionalist's two pennies[:D]