I think I discussed this already. Not specifically in a separate thread, but when comparing the 2. I am too lazy to look this up right now. But my conclusion is the 70D is more efficient overall, but I would get the S85D because of the HWY efficiency. Having a Model S means you will not need to worry about the city MPGE because you will have plenty of charge to make it anywhere in the city the whole day. However when you venture outside the city, this is when you need to worry about charge or the HWY efficiency.
Bases on these numbers, I am holding out for a CPO S85D or inventory S85D. I was originally considering the S70D, but it would do horribly compared to the S85D on the HWY.
I think the difference is the battery voltage of the two cars. The S70D uses the same voltage as the 60KWh battery which is lower than the 85KWh battery. I suspect Tesla optimize BOTH the CITY and HWY range at the lower voltage when choosing the different front and back motors. They just used the same setup for the S85D and tweaked the algorithm to use the more efficient motor at higher speed more often on the HWY to get the S85D HWY MPGE.