I would say that depends on what you plan to do, if your a sport jet or trainer jet 9 would be fine. If you dont mind using match boxes and Y harnesses 9 would do it for you as well. I save a lot of weight by not using all that stuff plus its more failure points. The more complex jets that have more features require more channels for things like speed brakes, canopy, canopy locks, stuff like that. I also like having enough channels for each servo so I can adjust end points, curves and things like that, but thats all personal liking stuff. Radios have come down quiet a bit and getting a 14 channel radio is not much more than a 8/9 channel, so pick what works for you and your plans.