Dual Ply will naturally always resist pinch flatting more than a single ply; I guess you question Andy is really whether you can get away with running single ply. The answer to that depends on where you ride, how you ride and what, if any, inner tube you're using.
To illustrate, I weigh 105kg, ride fast, aggressive and with little finesse; on Welsh trail centre tracks, the peak and lake district, I can't get away with a single ply rear if I'm using an inner tube; it has to be dual ply.
Around the north downs – loamy, rooty, sandy trails, single plys are fine.
Of course, tubeless is best of all worlds – lighter and with less chance of flatting, though not impossible.