205/huey : symmetrical aerofoil
412 : asymmetrical aerofoil. Huge loads, need hydraulics to make it happen. No hyd, no happen.
The reason symmetrical foils were picked originally was to minimise the forces needed to move the pitch (and for feedback) because otherwise the grips needed to be BIG and HEAVY, things which are not good for uptycopters with wooden blades and piston engines in the 40s/50s.
As technology improved, grips were made from lighter and stronger materials, and the designers could then progress from inefficient symmetrical shapes to more efficient funny shapes. But with the funnies came the need for stronger hydraulics and grips etc. With no hydraulics, it doesn't have the control power to move the pitch.
But the cheapies R22, 44, B206 stick with the symmetrics as it is cheaper and easier.
Still groundhog day, but we are off precession, and that is looking good for Bill Murray and Andie McDowell.