I have a Vltor MUR upper and an aero precision upper. For comparison, the Vltor seems stronger and the coating is slick thus making the action of the bolt a little smoother sounding. Now if it is actually smoother in movement, I have no idea. I have used BCM and Young Manu. Both sound a little different or feel a little different but I can't tell if grouping is any different. If I could have only one I guess I would choose Vltor upper but does it make a difference, nope. Barrel wise, spend some money and get a quality one. Never heard of Stretch 16.