Where does the extra performance (hp) come from? Same 85 kWh battery, right? How does the drive inverter do its thing? Does it sacrifice range?
A few % higher efficiency, IMO.
85 KWH is just the batteri size (ie tank volume). The performance model let you suck with bigger straws into the tank :-)
It's just a higher peak output drive inverter. Tesla has stated that a simliarly equipped MS 85 and MS P85, (read that as same weight and tire size) if driven in the exact same manner, will have the exact same range.
The difference is that, if you have a heavy foot, you will tend to waste a lot of energy accellerating really fast with the P85, which will cut your range.
Also, if you get the P85, I think you'd probably get the bigger wheels, which cut range somewhat.