DI is "mil-spec" and there are a lot of people that will argue that DI is better until the day they die ...or the US military adopts the piston system, whichever comes first.
Ever heard someone say, "If the piston system was better, Eugene Stoner would have made the original with it." Please... the military foot soldiers do not always have the best weapons available, just the most inexpensive that meets their standards.

