I've only dealt with DI systems, but from I read: the platform that the gas system is on is what matters. A piston on an AK-74 will work until doomsday, whereas a piston system built into the AR platform may not be as practical or effective.
I told the new me,
"Meet me at the bus station and hold a sign that reads: 'Today is the first day of the rest of your life.'"
But the old me met me with a sign that read: "Welcome back."
Who you are is not a function of where you are. -Off Minor