The M5 has standard BMW Assist, which uses a global positioning satellite (GPS) receiver and a cellular system to remotely unlock your doors if you lock your keys in, help track down your vehicle if it’s stolen or send emergency personnel to the scene if any airbags deploy. The S6 doesn’t offer a GPS response system, only a navigation computer with no live response for emergencies, so if you’re involved in an accident and you’re incapacitated help may not come as quickly.
Both the M5 and the S6 have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control and electronic stability systems to prevent skidding.
BMW pays for scheduled maintenance on the M5 for 4 years and 50,000 miles. BMW will pay for oil changes, tire rotation, lubrication and any other scheduled maintenance. Audi only pays for the first scheduled maintenance visit on the S6.
There are over 33 percent more BMW dealers than there are Audi dealers, which makes it easier should you ever need service under the M5’s warranty.
The M5’s 4.4 turbo V8 produces 140 more horsepower (560 vs. 420) and 94 lbs.-ft. more torque (500 vs. 406) than the S6’s 4.0 turbo V8.
In a Car and Driver race course test, the BMW M5 was clocked 4.6 seconds faster than the Audi S6 (185.2 sec. vs. 189.8 sec.).
Regenerative brakes improve the M5’s fuel efficiency by converting inertia back into energy instead of wasting it. The S6 doesn’t offer a regenerative braking system.
In heavy traffic or at stoplights the M5’s engine automatically turns off when the vehicle is stopped, saving fuel and reducing pollution. The engine is automatically restarted when the driver gets ready to move again. (Start/Stop isn’t accounted in present EPA fuel mileage tests.) The S6 doesn’t offer an automatic engine start/stop system.
The M5 has 1.3 gallons more fuel capacity than the S6 (21.1 vs. 19.8 gallons), for longer range between fill-ups.
The M5 offers optional heat-treated ceramic brake rotors, which last ten to twenty times as long as conventional cast iron rotors, don’t rust, don’t fade during repeated high speed braking, and their lighter weight contribute to better braking, handling and acceleration. The S6 doesn’t offer ceramic brake rotors.
For better traction, the M5 has larger tires than the S6 (F:265/40R19 & R:295/35R19 vs. 255/40R19).
The M5’s standard 295/35R19 rear tires provide better handling because they have a lower 35 series profile (height to width ratio) that provides a stiffer sidewall than the S6’s standard 40 series tires. The M5’s optional 295/30R20 rear tires have a lower 30 series profile than the S6’s optional 35 series tires.
For a smoother ride and more stable handling, the M5’s wheelbase is 2 inches longer than on the S6 (116.7 inches vs. 114.7 inches).
The M5’s front to rear weight distribution is more even (52.3% to 47.7%) than the S6’s (57% to 43%). This gives the M5 more stable handling and braking.
The M5 handles at .91 G’s, while the S6 pulls only .87 G’s of cornering force in a Car and Driver skidpad test.
As tested by Car and Driver while cruising at 70 MPH, the interior of the M5 is quieter than the S6 (69 vs. 70 dB).
The M5 has 2.5 cubic feet more passenger volume than the S6 (100.5 vs. 98).
The M5 has 3.3 inches more front headroom, .1 inches more front legroom, .8 inches more front shoulder room and .5 inches more rear headroom than the S6.
In poor weather, headlights can lose their effectiveness as grime builds up on their lenses. This can reduce visibility without the driver realizing. The M5 has standard headlight washers to keep headlight output high. The S6 doesn’t offer headlight washers.
To help keep rear passengers entertained, the M5 offers optional rear seat controls for the radio which can play a separate audio source. The S6 doesn’t offer rear seat audio controls.