ORIGINAL: chris1379
72 Mhz is fine if you don't have any issues. The reason for dual receivers on 2.4 GHz is it is more likely to get blocked or reflected. If the signal is lost momentarilly in a digital system like Spektrum, it can take several seconds for the receiver to lock back on to the transmitter. The extra receiver ensures that you always have a solid link in any orientation.
For older Spektrum, yes. The Futaba systems resync almost as quickly as a PCM radio.