That diesel mpg and torqueI'd say the A7 cause I'm biased when it comes to Audi.
but honestly, there really is no bad choice between these 3 models.
I think the S7 would be a fairer comparison with the 650 Gran Coupe and CLS550, just for performance, and power plant comparisons.
the standard A7 comes in either a Diesel or Gasoline V6 engine, that'd be comparable to the BMW 640 Gran Coupe that has the Inline-6 motor.