Make you're planes "fly better?" Only you can do that buddy....

with a 4 channel plane it will be the same AIRPLANE with a 30 dollar 4 channel radio set up like a used Jr Quattro... or with a 1200 dollar set up. Yea you can put in some mixing/expo/dual rates, but if you're flying a basic four channel I'm guessing trainer type plane.. all that stuff will not do much for you...

once you get into the big boys with flaps/landing gear or giant scale models then yeah you're going to need a pretty high end set up... I fly Spektrum DX7 and have absolutely no complaints... It can fly anything from a slow stick to a turbine with no problems and you'll probably never outgrow the DX7. I just got it and before the DX7 I flew with Futaba 6EX which was great for me for the past 6 years... but now have upgraded to 2.4 with the DX7.

I personally love the 2.4 now because there is no hassle of searching for the correct receiver/crystal/channel... just grab a Spektrum receiver, bind, and fly! I'd say if you're a beginner yeah pick up a nice set up just so it can grow with you, but no it's absolutely NOT required to be a great pilot... I still have my Avistar on a basic 4 channel radio... no digital anything, not 2.4, just a basic 72 mhz 4 channel radio and I have a blast with that plane!