You would be much better off with a 6 channel. Most now a days have some programming ability as well as dual rates and exponential. Another nice feature of programmable controllers is something called mixing.

Dual Rates: The ability to adjust the sensitivity of your plane in flight.

Exponential: A more advanced version of Dual Rates. As you move the stick from center, the more sensitive it becomes.

Mixing: Being able to control 2 servos with one action (example: Rudder and elevator, or Flaps with elevator, or ailerons with rudder)

For a person just getting into the hobby, you might not need these features, but as you build more complex planes, they will become quite nice. The extra channels are nice for gear retracts, smoke systems, dual ailerons and many others.