Don't underestimate the value of knowing you at least have something that flies. I spent the last few months trying to get a small electric delta (http://uavfun.tripod.com/temp/IMAGE0007.JPG) to fly. I never really got a chance to work on the electronics. It took ages to get it to fly at all; it started out VERY unstable. Then I changed some small little thing yesterday (I don't even know what) and it went from being a little wobbly to not flying at all. I wasted a LOT of time fixing all the electronic parts that got broken every time it crashed. There was also no way it would lift the little digital camera I wanted to put in it. It just wasn't worth it; I'll make a more conventional plane and move everything to that.

What are you planning to use for sensors and so on to tell what the vehicle is doing? It takes quite a bit (see http://autopilot.sourceforge.net/ for an example). With a plane you can 'cheat' a little bit (for example, measuring angle of attack and monitoring altitude instead of keeping track of pitch), but that won't work with a heli. You will need to constantly keep track of pitch and roll at the very least, and probably also heading and altitude.