Generally, the larger a plane is, the easier it is to fly. Many model aircraft pilots are also full-scale pilots and they find the sport a challenge. You must rely on your eyes, ears and instincts to tell you what your gut or instrumentation would in a full-scale plane. Kinda like Golf. Some like to build model aircraft, some like to fly them, some like to do both, some are into competition, some are into the engineering challenge, some want to build detailed scale replicas of full-scale aircraft and some are just looking for any excuse to get away from their wives on the weekends.
Planes are easier to fly and less expensive to start with.
They're also less complicated. Besides, if God had meant for Heli's to fly, he would've given them wings. They make multi-channel radios up to nine. These extra channels can be used for extra scale controls such as retractable landing gear and flaps. A basic radio system's components consist of a transmitter which you use to control the plane, a receiver which is installed in the plane and picks up your transmitter signal and decodes it into control signals for the servos.