Helicopter buying considerations

Backordered the Sparkfun parts. Now to look at a helicopter.

There are lots of sites with buying guides for beginner fliers. But I think what I'm looking for is slightly different because I'm looking for a helicopter that will be easy to close a control loop around, which may not necessarily be one that is easy to fly by hand. Or will I need to learn how to fly it by hand before handing it over to the control system? I hope not...

For one, bigger helicopters are supposed to be easier to fly because everything happens more slowly. That might not be as much of an issue with the control system. Not only is its reaction time much better than mine, it will have access to acceleration data (an idea: get another 2-axis accelerometer and mount it a distance away from the main IMU, to get angular acceleration) whereas a human operator only sees position.

Now, what about fixed vs. collective pitch? Cost and crashworthiness are both still extremely relevant, which suggests fixed pitch. What about the controllability? Fixed has one fewer control input, and the variable rotor speed is going to wreak havoc on the cyclic control transfer functions, which I suspect are strongly influenced by rotor speed (may need to install a rotor tachometer).

I guess we'll look more closely at the cost, then. It may also be important to get one with separate electronics so that I don't have to hack into some integrated receiver/motor controller module. And for this, the dumber the electronics, the better.