...whereas Airbus opted to make it harder for the computers to fail in the same way. Both completely valid ways of solving the problem...
Question:
Graceful degradation is the same in both?
FM (frquency modulation) has the so called "threshold effect". Up to a certain level, everything is fine (excellent Signal to noise ratio).
Below a certain level worms, dominate the scene. So aviation uses AM.
Doppler effect also was a factor in the selection