ORIGINAL: HarryC
Each PCM system is different but a typical protocol is to split the data into two packets - two packets of four channels rather than one frame of 8 channels as PPM does. However each PCM packet still has a header with lots of data to identify that packet and if that header gets blasted the packet is failsafed. On the face of it that seems better, if the interference is very very short lived then you lose 4 channels in that packet rather than 8 channels until the next PPM frame, but since PCM runs so slowly (apart from the new 14MZ), the actual time that control is lost until regained is pretty much similar to PPM. In reality you are going to struggle to notice the difference between IPD and PCM when interference strikes.
I normally use PPM simply because I have several of the PPM receivers but only one PCM receiver.
I recently had a severe interference that I never did isolate. I changed all components except the wiring. I could get about 100' with the engine off and only about 10' range with it running. I put in the PCM receiver and had 300' range with the engine running. I concluded that the PCM receiver is a hell of a lot better than the PPM receiver. Unfortunately I didn't think to try the IPD receiver