RE: Synthesized TXs?
I think it's a good idea for a number of reasons, which may or may not apply to you.
I do instruction, and a number of my students have Hitec or Futaba transmitters. I have a Prism with the synth module, and can set it up to train them and they can use their own transmitter as the student box. Or they can use my Futaba SS6 as a buddy box, and my Prism can fly their JR or Airtronics equipped trainer.
I wound up with so many planes I wanted the 99 model memory of the Polk Tracker II. Works great for me. I see they're going to sell a Tracker III, with a trainer port and other new features, so I'll probably get one of them and sell my Tracker II.
If you have one plane, or two, and plan to stick with them (say, to fly pattern) you really don't need a synth... but you might want to buy an extra module on a different frequency, and an RX crystal. That way you have a couple choices, at contests and such.
Good luck,
Dave Olson