I'm not jumping in to say for or against PCM. But I do want to clear up one point. There are two types of modulation that is used PPM and PCM. BOTH of these use FM as the transport signal. Many get confused and thing that they are choosing between FM or PCM, but in reality PCM uses FM. FM is how the signal is transmitted from the transmitter to the receiver. PPM or PCM is the language that the radio speaks to the plane with. There is a bit more involved with the differences between PPM and PCM, but I just wanted to point out that no matter what modulation you use it's still an FM radio.

Ken