In the past twenty years hundreds of infants and young children have died after being left in vehicles, usually by accident. When turning the vehicle off, drivers of the M5 are reminded to check the back seat if they opened the rear door before starting out. The S7 doesn’t offer a back seat reminder.
Over 200 people are killed each year when backed over by motor vehicles. The M5 has standard Active Park Distance Control that uses rear sensors to monitor for objects to the rear and automatically applies the brakes to prevent a collision. The S7 doesn’t offer automatic braking for stationary objects directly to the rear.
The M5 has a standard blind spot warning system that uses sensors to alert the driver to objects in the vehicle’s blind spots where the side view mirrors don’t reveal them and moves the vehicle back into its lane. A system to reveal vehicles in the S7’s blind spot costs extra.
To help make backing out of a parking space safer, the M5 has standard Cross Traffic Warning, helping the driver avoid collisions. Audi charges extra for Rear Cross-Traffic Assist on the S7.
Both the M5 and the S7 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, all wheel drive, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, post-collision automatic braking systems, daytime running lights, lane departure warning systems, rearview cameras and driver alert monitors.
The BMW M5 weighs 793 to 933 pounds more than the Audi S7. The NHTSA advises that heavier cars are much safer in collisions than their significantly lighter counterparts.