Depends first of all on the driver, if the driver of the RS4 knows how to drive it and was in say 2nd coming out of the roundabout and then floored it then the eddy would have an hard time catching up, but if you caught him out and he was in 3rd it would be a different matter
The RS4 needs to be on the boil all the time to go fast, if you try put your foot down in 3rd-4th gear at around 30-40mph it tends to take a bit to get going but above that its quite a weapon
but then that's big NA engine cars for you.
Darren