I don't know if you have a local hobby store locally (?) but if you can, get out and get your hands on the radios you're looking at before you buy. Most modern radios, especially by the time you get up to the 7 channel range, are all very good, and the real difference is features and how the programming works. You can always go to your local field and ask what folks think about the radios they're using. Personally, I like Futaba, but JR seems very nice, but Hitec makes a nice radio too, as does Airtronics.

As far as PCM, it's a different way of encoding the signals to the servos. PCM and regular PPM are both transmitted in exactally the same way. PCM is more reliable, but if you don't actually NEED it, don't bother with it.

Andy