Not that it really matters, I use a Futaba 9 ZAP. It has 8 fully proportional channels and a 9th on/off channel (for on/off tasks like smoke or retracts.)

I'm not sure if there is a "balance." If you need more channels to fly the plane of your dreams, you need the channels. If you want to fly a heli with collective pitch, you really need 5 channels, etc.

Like I pointed out before, probably most planes can be flown on a 4 ch transmitter. You may have to use a Y-harness of some type, but it still can be done. Adding an additional 2 channels really simplifies things on planes that use dual ailerons/dual elevators. And, you'll need an extra channel if you want flaps or retracts or smoke or what ever.

The "average" RC pilot probably uses a 4ch or 6ch radio as this is all they really need. However, what sells many on the higher channel radios isn't actually the channels. While the pilot may make use of the extra channels, it is the advanced programming features typically only found in the higher channel radios that is the main selling point.

For example, what sold me on my 9ZAP wasn't the 9 channels. I selected the ZAP because of the flexibility in the radio and a programming feature called conditions. The 9 channels however are nice... sometimes I wish I had more, but it was really the mixing the pushed me to buy the radio. I ran out of mixers on my 6XAS before I needed a 7th channel (6XAS has 6 channels.)

Cheers