RE: stuppid newb Q
In my opionion the only advantages of PCM is the faisafe ability, and servo resolution.(for lack of a better term)
in the case of FM lets say you get some radio interference, the servos may go haywire and glitch all over.
in the case of PCM, you get radio interference, the servos will "hold" until a radio link is re-established, also most PCM failsafe systems have either the hold failsafe method OR you can select a specific positions for the servos during failsafe.
lets compare servo resolution, lets say FM has 512 servo positions throughout the stick movement on an axis, and PCM has 1024 making for more precise movements.
I have seen ads for futaba "2048 PCM" I think this would be even more precise.