If you hop right into the 70D after a p85d, yes huge diff. However, that's not a "need" issue. I used to have a Saturn Sky turbo (5.5s car), and the MS 60 feels light years faster. You can get a good idea how fast 50-80 will be from the
Tesla Model S 60 kWh vs Tesla Model S 85 kWh Performance | DragTimes.com Drag Racing, Fast Cars, Muscle Cars Blog comparison. You'll notice the 60 lags by only 10mph (102 versus 112) against the P85 in the 1/4 mile. The 60 is faster than the twin turbo 535xi in the quarter by a couple tenths. Not to mention you don't have to wait for any turbo lag and downshifting when passing.
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Even more directly, the 535xi takes 3.8s to go from 50-70, versus 3.1 for the 70D. The BMW is already a very competent autobahn bred passer.
2015 Tesla Model S 70D Instrumented Test Car and Driver
For reference here is same mag reviewing the 535xi and other luxury sedans. Notice all are slower than the 70D from 50-70.
2014 Cadillac CTS 3.6 vs. 2014 Audi A6 3.0T, 2014 BMW 535i xDrive, 2014 Mercedes-Benz E350 Comparison Tests - Page 6 - Car and Driver