The RS6 was miles ahead in speed, torque, grip and ride quality. Got to say the interior of the RS6 with the new style screen flip out from the dash was better too.
Both test drives were unaccompanied for 1 hour, and both myself and a friend were in agreement, the overtaking ability of the RS6 is unbelievable, 1 or 2 cars in the RS4 was 3-4 or more in the RS6.
There was no sell at all from Audi, just food, drink and advice from the Audi professional drivers (who could take you out if you preferred).
Loved the whole experience and I'm counting the days til i can upgrade from the C6 to the C7 RS6. What a car.

Carl