The M-Class’ front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The Cayenne doesn’t offer pre-crash pretensioners.
An active infrared night vision system optional on the M-Class helps the driver to more easily detect people, animals or other objects in front of the vehicle at night. Using an infrared camera and near-infrared lights to detect heat, the system then displays the image on a monitor in the dashboard. The Cayenne doesn’t offer a night vision system.
The M-Class’ driver alert monitor detects an inattentive driver then sounds a warning and suggests a break. According to the NHTSA, drivers who fall asleep cause about 100,000 crashes and 1500 deaths a year. The Cayenne doesn’t offer a driver alert monitor.
The M-Class has standard mbrace, 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 Cayenne 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 M-Class and the Cayenne have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, front and rear seatbelt pretensioners, height-adjustable front shoulder belts, plastic fuel tanks, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding and available all wheel drive.
For its top level performance in all IIHS frontal, side, rear impact and roof-crush tests, and its standard front crash prevention system, the Insurance Institute for Highway Safety grants the M-Class its highest rating: “Top Pick Plus” for 2014, a rating granted to only 48 vehicles tested by the IIHS. The Cayenne has not been tested, yet.
The Mercedes M-Class has a better fatality history. The M-Class was involved in fatal accidents at a rate 14% lower per vehicle registered than the Cayenne, according to the Insurance Institute for Highway Safety.
There are over 55 percent more Mercedes dealers than there are Porsche dealers, which makes it much easier should you ever need service under the M-Class’ warranty.
J.D. Power and Associates’ 2014 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that Mercedes vehicles are more reliable than Porsche vehicles. J.D. Power ranks Mercedes second in reliability, above the industry average. With 21 more problems per 100 vehicles, Porsche is ranked 9th.
The M-Class has a standard automatic load leveling suspension to keep ride height level with a heavy load or when towing. The Cayenne doesn’t offer a load leveling suspension.
For greater off-road capability the M-Class Airmatic has a greater minimum ground clearance than the Cayenne Turbo (11.2 vs. 10.75 inches), allowing the M-Class to travel over rougher terrain without being stopped or damaged.
The M-Class has 2.4 inches more rear legroom and 1.7 inches more rear shoulder room than the Cayenne.
The M-Class has a much larger cargo area with its rear seat up than the Cayenne with its rear seat up (38.2 vs. 23.7 cubic feet). The M-Class has a much larger cargo area with its rear seat folded than the Cayenne with its rear seat folded (80.3 vs. 62.9 cubic feet).
If the windows are left down on the M-Class the driver can raise them all using the key in the outside lock cylinder or the keyless remote; on a hot day the driver can lower the windows. The driver of the Cayenne can only operate the windows from inside the vehicle, with the ignition on.
When the M-Class with available tilt-down mirrors is put in reverse, the passenger rearview mirror tilts from its original position. This gives the driver a better view of the curb during parallel parking maneuvers. Shifting out of reverse puts the mirror into its original position. The Cayenne’s mirror doesn’t automatically adjust for backing.
Optional Mercedes-Benz Apps for the M-Class allows the driver and passengers access to select programs on their smartphones, including playing internet radio stations, finding fuel prices at nearby service stations, searching the internet and other connected activities without taking their eyes off the road or their hands from the wheel. The Cayenne doesn’t offer factory integrated smartphone program access.
The M-Class offers an optional 115-volt a/c outlet in the cargo area, allowing you to recharge a laptop or run small household appliances without special adapters that can break or get misplaced. The Cayenne doesn’t offer a house-current electrical outlet.
The M-Class’ optional Active Parking Assist can parallel park or back into a parking spot by itself, with the driver only controlling speed with the brake pedal. The Cayenne doesn’t offer an automated parking system.
According to The Car Book by Jack Gillis, the M-Class is less expensive to operate than the Cayenne because typical repairs cost much less on the M-Class than the Cayenne, including $909 less for an alternator and $99 less for front brake pads.
Consumer Reports® recommends both the Mercedes M-Class and the Porsche Cayenne, based on reliability, safety and performance.
The Mercedes M-Class outsold the Porsche Cayenne by almost three to one during the 2014 model year.