Buddy box--only needs to be four channels to control the main control surfaces. All other features, if present (i.e. flaps, gear, etc.) shouldn't be a consideration to the student anyway.

with JR, DO NOT take out the crystal in the buddy box. There is no need, and I'm not even sure if it will work. Just don't turn the buddy box on. When you plug the trainer cord into the buddy box, it will power up immediately, (if the battery is charged), but will not broadcast a signal. It simply sees the master radio as it would DSC--direct servo control, and sends signals through the cord, and not through the air. With JR, you have to have a charged battery in the buddy box. With futaba, the buddy box draws power from the master--so no battery is required.