Well, in AR-15 5.56 format mags, both PMAGS and the Lancer L-5 mags are repeatedly in the top 5 lists of best mags. I would say, if you plan on keeping them loaded, then the Lancers because of the metal reinforcement.
People love PMAGS but the plastic feed lips do have a reputation of not holding up as well as the old steel and aluminum mags. There is a polymer mag out there with metal feed lips. It might be the Lancers mentioned above. I run stainless ASC mags myself.