the heli and air plane version have one major difference... the throttle ratchet. The airplane version will have a throttle ratchet, simply put it indexes the throttle stick on small teeth that help hold it in place, this will make hovering a heli damn near impossible... so they leave it off the heli version. if you already had the air plane version you can loosen or remove the ratchet to fly heli's. you will also find some switch location/assignments are different but that's usually not a problem unless your use to flying the switches in a certain configuration. The software is the same in both types so each will work for plane's ,heli's and sailplanes as far as programing goes. personally I find the throttle ratchet useless and more of a PIA than a help... both of my 9C's have them removed and I only use one to fly my heli
if money is not an issue and you plan on sticking with the hobby buy the 9303... either will do but the 9303 has more features you may find you need later on.
John