I think one of the problems is that rudder pedals just have one axis that each pedal gives you +/-, whereas good driving pedals have three. I tried once to set up my G29 pedals to do this but it never really worked. Also, you would miss the toe brakes. I ended up getting some TFRP ones, which were great for fixed wing, but not quite sensitive enough for helicopters.
The VKB ones are more expensive and lack a toebrake (although you can do a software workaround) but are fantastic for helicopter flight.
