Just in terms of power, these two seem very similar. The BMW produces 626 horsepower (467 kilowatts and 553 pound-feet (750 Newton-meters) of torque from a 4.4-liter twin-turbo V8. The Audi has 592 hp (441 kW) and 590 lb-ft (800 Nm) from a twin-turbo 4.0-liter V8. Both are all-wheel drive.
The major differentiating factor is weight. The M5 CS is 4,189 pounds (1,900 kilograms), but the RS7 is a heftier 4,718 pounds (2,140) kilograms. As you might expect, 529 pounds (240 kilograms) makes a significant difference in a drag race.
In the first drag race, the Audi initially shows its strength by getting a lead off the line. The RS7 pulls ahead, and then the M5 CS finds traction. The BMW rockets ahead, and leaves the Audi in its wake. The RS7 is only 0.08 seconds slower to 62 miles per hour (100 kilometers per hour), but it’s a shocking 2.28 seconds behind in the sprint from 62 mph to 124 mph (100 kph to 200 kph).
The second race is even more in the BMW’s favor. The M5 CS gets a great start and rockets away. According to the numbers, the RS7 was 0.32 seconds slower to 62 mph this time and 1.71 seconds slower for the acceleration from 62 mph to 124 mph.
Finally, there’s a race from a roll where the Audi’s extra torque might give the RS7 an advantage. It doesn’t. The M5 CS simply accelerates away, and the sedan from the Four Rings can’t keep up.