I say "radio control" for the same reasons Minnflyer enumerates. For some reason, "remote control" sounds more toy-like, and for me invokes memories of sitting next to the slot-car track, controller in hand, watching my car go 'round and 'round....and 'round.

Radio control sounds more high-tech. I can envision myself as a highly-skilled military technician sitting in front of a video screen inside a highly guarded and bulletproof bunker, getting ready to nuke Osama with a Predator on the other end of my joystick

Then I come out of my daydream, just in time to pull my Piper Cub out of its uncontrolled dive just before I plant it in the bushes.