If you're looking for "home-style" (bready) pizza crust, cast iron works fine; if you're looking for a NY/Neapolitan-style crust, stick with a stone. I cook pizza over live coals on camping trips all the time, and IMO, cast iron pans are a great substitute for dark steel deep dish pans (in fact, in some ways I prefer cast iron pans for deep dish). My experience with NY/American/Neapolitan style crusts is that they come out bread-ier and less crusty than on a stone. My guess is that with cast iron most of the moisture in the dough "boils" up through the dough and out the top of the pizza instad of being drawn out of the bottom like it is on a stone.