The 9C transmitter can shift back and forth through it's settings between PPM (FM) and PCM modulation. What you are paying for is the extra for a PCM receiver. The receivers come only in PPM or PCM and you can't switch them between the two modulations like the Transmitter. I think you also get better servos with the PCM version but and not sure on that.

Just starting out you should be fine with PPM and can always sell your receiver and buy a PCM version at a later date if you decide you need to.