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The C-Class Cabriolet has standard front and rear seat side-impact airbags and head airbags, which act as a forgiving barrier between the passengers and the door. Combined with high-strength steel door beams this system increases protection from broadside collisions. The A3 Cabriolet doesn't offer rear-seat side-impact airbags, only ones for front seat occupants.
The C-Class Cabriolet offers an optional Surround View System to allow the driver to see objects all around the vehicle on a screen. The A3 Cabriolet only offers a rear monitor and front and rear parking sensors that beep or flash a light. That doesn’t help with obstacles to the sides.
The C-Class Cabriolet’s 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 A3 Cabriolet doesn’t offer a driver alert monitor.
The C-Class Cabriolet has standard Mercedes-Benz Emergency Call, which uses a global positioning satellite (GPS) receiver and a cellular system to get turn-by-turn driving directions, 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 A3 Cabriolet 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 C-Class Cabriolet and the A3 Cabriolet have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger knee airbags, side-impact head airbags, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, daytime running lights, rearview cameras, available all wheel drive, lane departure warning systems and rear cross-path warning.
There are over 26 percent more Mercedes dealers than there are Audi dealers, which makes it easier should you ever need service under the C-Class Cabriolet’s warranty.
J.D. Power and Associates’ 2019 Initial Quality Study of new car owners surveyed provide the statistics that show that Mercedes vehicles are better in initial quality than Audi vehicles. J.D. Power ranks Mercedes 12th in initial quality. With 12 more problems per 100 vehicles, Audi is ranked 22nd.
The C-Class Cabriolet’s 2.0 turbo 4-cylinder produces 71 more horsepower (255 vs. 184) and 52 lbs.-ft. more torque (273 vs. 221) than the A3 Cabriolet 40 TSFI’s standard 2.0 turbo 4-cylinder. The C-Class Cabriolet’s 2.0 turbo 4-cylinder produces 27 more horsepower (255 vs. 228) and 15 lbs.-ft. more torque (273 vs. 258) than the A3 Cabriolet 45 TSFI’s optional 2.0 turbo 4-cylinder.
The C-Class Cabriolet has 4.2 gallons more fuel capacity than the A3 Cabriolet 40 TFSI’s standard fuel tank (17.4 vs. 13.2 gallons), for longer range between fill-ups. The C-Class Cabriolet has 2.9 gallons more fuel capacity than the A3 Cabriolet 45 TFSI Quattro’s standard fuel tank (17.4 vs. 14.5 gallons).
A nine-speed automatic is standard on the Mercedes C-Class Cabriolet, for better acceleration and lower engine speed on the highway. Only a seven-speed automatic is available for the A3 Cabriolet.
For better stopping power the C-Class Cabriolet’s brake rotors are larger than those standard on the A3 Cabriolet:
The C-Class Cabriolet’s standard front and rear disc brakes are vented to help dissipate heat for shorter stops with less fading. The rear discs on the A3 Cabriolet are solid, not vented.
The C-Class Cabriolet stops shorter than the A3 Cabriolet:
70 to 0 MPH
Car and Driver
For better traction and acceleration, the C-Class Cabriolet has larger rear tires than the A3 Cabriolet (245/40R18 vs. 225/45R17). The C-Class Cabriolet’s rear tires are larger than the largest rear tires available on the A3 Cabriolet (245/40R18 vs. 235/35R19).
The C-Class Cabriolet’s standard 245/40R18 rear tires provide better handling because they have a lower 40 series profile (height to width ratio) that provides a stiffer sidewall than the A3 Cabriolet’s standard 45 series tires.
For better ride, handling and brake cooling the C-Class Cabriolet has standard 18-inch wheels. Smaller 17-inch wheels are standard on the A3 Cabriolet.
Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires standard on the C-Class Cabriolet can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The A3 Cabriolet doesn’t offer run-flat tires.
The C-Class Cabriolet’s drift compensation steering can automatically compensate for road conditions which would cause the vehicle to drift from side to side, helping the driver to keep the vehicle straight more easily. The A3 Cabriolet doesn’t offer drift compensation steering.
For a smoother ride and more stable handling, the C-Class Cabriolet’s wheelbase is 9.6 inches longer than on the A3 Cabriolet (111.8 inches vs. 102.2 inches).
The C 300 Cabriolet handles at .94 G’s, while the A3 Cabriolet pulls only .86 G’s of cornering force in a Car and Driver skidpad test.
The front grille of the C-Class Cabriolet uses electronically controlled shutters to close off airflow and reduce drag when less engine cooling is needed. This helps improve highway fuel economy. The A3 Cabriolet doesn’t offer active grille shutters.
The C-Class Cabriolet has 2.3 cubic feet more passenger volume than the A3 Cabriolet (81.3 vs. 79).
The C-Class Cabriolet has 1.4 inches more front headroom, .8 inches more front legroom, .1 inches more rear legroom and 6 inches more rear shoulder room than the A3 Cabriolet.
With its convertible body style, locking rear seatbacks and remote trunk release lockout, the C-Class offers cargo security. The A3 Cabriolet’s non-lockable folding seat and non-lockable remote release defeat cargo security.
The engine in the C-Class Cabriolet is mounted longitudinally (North-South), instead of sideways, as in the A3 Cabriolet. This makes it easier to service and maintain, because the accessory belts are in front.
J.D. Power and Associates surveys of service recipients show that Mercedes service is better than Audi. J.D. Power ranks Mercedes fifth in service department satisfaction. With a 13% lower rating, Audi is ranked 8th.
The C-Class Cabriolet has a standard remote vehicle starting system, so the vehicle can be started from inside the driver's house. This allows the driver to comfortably warm up the engine before going out to the vehicle. The climate system will also automatically heat or cool the interior. The A3 Cabriolet doesn’t offer a remote starting system.
When three different drivers share the C-Class Cabriolet, the memory system makes it convenient for all three. Each setting activates different, customized memories for the driver’s seat (memory seat optional for the front passenger), steering wheel position and outside mirror angle. The A3 Cabriolet doesn’t offer a memory system.
The C-Class Cabriolet’s standard easy entry system raises the steering wheel, making it easier for the driver to get in and out. The A3 Cabriolet doesn’t offer an easy entry system.
The C-Class Cabriolet offers an optional heads-up display that projects speed and navigation instruction readouts in front of the driver’s line of sight, allowing drivers to view information without diverting their eyes from the road. The A3 Cabriolet doesn’t offer a heads-up display.
The C-Class Cabriolet’s standard power windows have a locking feature to keep children in the rear seat from operating them, but the driver can still raise and lower all of them with the lock engaged. Audi does not offer a locking feature on the A3 Cabriolet’s standard power windows.
In case of a sudden change of weather, the C-Class Cabriolet has a standard remote convertible top that can be raised from a distance to protect the interior of the vehicle from damage. The A3 Cabriolet doesn’t offer a remote top, so the driver will have to run to the car, get in, turn the ignition on and raise the top to prevent the interior from being damaged.
The C-Class Cabriolet’s power window, power lock, power mirror and cruise control switches are lit from behind, making them plainly visible and easier to operate at night. The A3 Cabriolet’s cruise control switches are unlit, making them difficult to find at night and operate safely.
To help drivers see further while navigating curves, the C-Class Cabriolet offers optional adaptive headlights to illuminate around corners automatically by reading vehicle speed and steering wheel angle. The A3 Cabriolet doesn’t offer cornering lights.
When the C-Class Cabriolet 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 A3 Cabriolet’s mirror doesn’t automatically adjust for backing.
Optional air-conditioned seats in the C-Class Cabriolet keep the driver and front passenger comfortable and take the sting out of hot seats in summer. The A3 Cabriolet doesn’t offer air-conditioned seats.
On extremely cold winter days, the C-Class Cabriolet’s optional heated steering wheel provides comfort, allowing the driver to steer safely and comfortably before the car heater warms up. The A3 Cabriolet doesn’t offer a heated steering wheel.
The C-Class Cabriolet’s optional Active Parking Assist can parallel park or back into a parking spot by itself, stopping and changing direction automatically. The A3 Cabriolet doesn’t offer an automated parking system.
The Mercedes C-Class comes in coupe, convertible and sedan bodystyles; the Audi A3 isn’t available as a coupe or sedan.
Consumer Reports® recommends both the Mercedes C-Class Cabriolet and the Audi A3 Cabriolet, based on reliability, safety and performance.
J.D. Power and Associates rated the C-Class Cabriolet first among compact premium cars in owner reported satisfaction. This includes how well the vehicle performs and satisfies its owner’s expectations. The A3 Cabriolet isn’t in the top three in its category.
The Mercedes C-Class outsold the Audi A3/S3 by almost six to one during the 2019 model year.
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