I'm getting great mileage on my X 75D...
after 6300miles I'm at 292 wh/m.
So far this month (now that the tires are worn in for 6000 miles)... 287.7miles at
235wh/m.
My commute on friday I managed 231wh/m for the 31.1mile roundtrip.
(As you can see in the photo from current trip... my start and end points for my commute differ by 1000ft, so only round trip numbers make sense)
Generally the mild weather has helped for the X, but trips to Tahoe and Carmel have made it worse, and I've also done a couple of hundred miles of bike racks with bikes in that 292 wh/m figure. I'm going to destroy my November figures with a ski trip next weekend.
Lifetime on our S P85 so far is 291 wh/m for 52000miles. For the first few months I was over 300wh/m.
My best ever commute with that was 225wh/m.
(My commute hasn't changed for over 3 years)
So yes I'd suggest that considering similar age of cars (and specifically tires) that in real world conditions (particularly commuting) it seems that the X 75D with stock 20" wheels is a touch better than a 2013 S P85 with stock 19" wheels.
Hence I expect that in 50000 miles my lifetime average should be about 290-300wh/m depending on how my commute and trips change in that time.