Hi.
I have used the Wisycom MRK960 many times over the last year, and have experienced the walkie problems myself. Read what Larry from Lectro have written about wideband vs. narrowband amplifiers and receivers. When you have active wideband amps on the sharkfins going into wideband multicouplers, wideband amps for the RF link out on the receiver etc. you have a lot of potential for generating intermod. I do not have experience with the MRK42.
The thing with analogue compander IC's is they are not perfect devices, Sennheiser spent a lot of work to model the HiDyn system for their DSP based 3732 receiver. A good test is instruments with a lot of lowend content and listening for signs of tracking errors.