RWD is more efficient because it doesn't use the idler gear (internal spur/pinion), but at this gearing you are close to riding the RPM limit most of the time so it should be close to the same speed. Allowing higher gear ratios would swing the favor towards RWD further. I think you chose an excellent ratio for rwd/fwd/awd to race with good parity.
I had some assistance picking out the gearing ;-).
Thanks EMU.
Cheers,
Jim