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 C-Class Sedan are reminded to check the back seat if they opened the rear door before starting out. The A3 doesn't offer a back seat reminder.

The C-Class Sedan has a standard front seat center airbag, which deploys between the driver and front passenger, protecting them from injuries caused by striking each other in serious side impacts. The A3 doesn't offer front seat center airbags.

With its available Active Brake Assist with Cross-Traffic Function, the Mercedes C-Class Sedan is better at preventing collisions with pedestrians than the Audi A3, according to the Insurance Institute for Highway Safety:

The C-Class Sedan'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 doesn't offer a driver alert monitor.

Both the C-Class Sedan and the A3 have standard driver and passenger frontal airbags, front side-impact airbags, driver knee airbags, side-impact head airbags, front seatbelt pretensioners, height adjustable front shoulder belts, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, crash mitigating brakes, post-collision automatic braking systems, daytime running lights, blind spot warning systems, rearview cameras, rear cross-path warning, available all wheel drive, lane departure warning systems and around view monitors.

The Mercedes C-Class Sedan has achieved the Insurance Institute for Highway Safety's (IIHS) highest rating of “Top Safety Pick Plus” for the 2025 model year. This distinction is based on its exceptional performance in IIHS' rigorous battery of safety tests. Specifically, it earned a “Good” rating in the latest, more stringent moderate overlap front crash test, a “Good” result in the updated side impact test, and an “Acceptable” to “Good” score in the revised pedestrian crash prevention test. The A3 is not even a standard “Top Safety Pick” for 2025.

There are over 25 percent more Mercedes dealers than there are Audi dealers, which makes it easier should you ever need service under the C-Class Sedan's warranty.

J.D. Power and Associates' 2025 Initial Quality Study of new car owners surveyed provide the statistics that show that Mercedes vehicles are better in initial quality than Audi vehicles. With 59 fewer problems per 100 vehicles, JD Power ranks Mercedes higher than Audi.

J.D. Power and Associates' 2025 survey of the owners of three-year-old vehicles provides the long-term dependability statistics that show that Mercedes vehicles are more reliable than Audi With 30 fewer problems per 100 vehicles in the first three years of ownership, J.D. Power ranks Mercedes higher than Audi.

The C-Class Sedan's 2.0 turbo 4-cylinder hybrid produces 54 more horsepower (255 vs. 201) and 59 lbs.-ft. more torque (295 vs. 236) than the A3's 2.0 turbo 4-cylinder hybrid.

As tested in Car and Driver the Mercedes C-Class Sedan is faster than the Audi A3:

The C-Class Sedan has 2.9 gallons more fuel capacity than the A3 (17.4 vs. 14.5 gallons), for longer range between fill-ups.

In its Green Vehicle Guide, the U.S. Environmental Protection Agency (EPA) rates the Mercedes C-Class Sedan higher (7 out of 10) than the Audi A3 (6). This means the C-Class Sedan produces up to 1.1 pounds less smog-producing pollutants than the A3 every 15,000 miles.

A nine-speed automatic is standard on the Mercedes C-Class Sedan, for better acceleration and lower engine speed on the highway. Only a seven-speed automatic is available for the A3.

For better stopping power the C-Class Sedan's brake rotors are larger than those on the A3:

The C-Class Sedan'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 are solid, not vented.

The C-Class Sedan stops much shorter than the A3:

For better traction and acceleration, the C-Class Sedan has larger standard rear tires than the A3 (245/40R18 vs. 225/45R17). The C-Class Sedan's optional rear tires are larger than the largest rear tires available on the A3 (255/35R19 vs. 225/45R17).

The C-Class Sedan'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's standard 45 series tires. The C-Class Sedan's optional 255/35R19 rear tires have a lower 35 series profile than the A3's optional 40 series tires.

For better ride, handling and brake cooling the C-Class Sedan has standard 18-inch wheels. Smaller 17-inch wheels are standard on the A3. The C-Class Sedan's optional 19-inch wheels are larger than the 18-inch wheels optional on the A3.

Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires available on the C-Class Sedan can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The A3 doesn't offer run-flat tires.

The C-Class Sedan'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 doesn't offer drift compensation steering.

For a smoother ride and more stable handling, the C-Class Sedan's wheelbase is 9.3 inches longer than on the A3 (112.8 inches vs. 103.5 inches).

For better handling and stability, the track (width between the wheels) on the C-Class Sedan is 1.6 inches wider in the front and 3.2 inches wider in the rear than on the A3.

The C 300 Sedan 4MATIC handles at .91 G's, while the A3 Premium Plus pulls only .89 G's of cornering force in a Car and Driver skidpad test.

The design of the Mercedes C-Class Sedan amounts to more than styling. The C-Class Sedan has an aerodynamic coefficient of drag of .24 Cd. That is significantly lower than the A3 (.29) and many sports cars. A more efficient exterior helps keep the interior quieter and helps the C-Class Sedan get better fuel mileage.

Because it has more passenger and cargo room, the EPA rates the C-Class Sedan a Compact car, while the A3 is rated a Subcompact.

The C-Class Sedan has 6 cubic feet more passenger volume than the A3 (93 vs. 87).

The C-Class Sedan has 3.2 inches more front headroom, .5 inches more front legroom, 1.5 inches more front shoulder room, .9 inches more rear headroom, .8 inches more rear legroom and 2.6 inches more rear shoulder room than the A3.

The C-Class Sedan has a larger trunk than the A3 (11.6 vs. 10.9 cubic feet).

Pressing a switch automatically lowers the C-Class Sedan's rear seats, to make changing between passengers and cargo easier. The A3 doesn't offer automatic folding seats.

With its sedan body style, valet key, locking rear seatbacks and remote trunk release lockout, the C-Class offers cargo security. The A3's non-lockable folding seat and non-lockable remote release defeat cargo security.

The engine in the C-Class Sedan is mounted longitudinally (North-South), instead of sideways, as in the A3. This makes it easier to service and maintain, because the accessory belts are in front.

The C-Class Sedan 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 doesn't offer a remote starting system.

Unlike the driver-only memory seat and mirrors optional at extra cost in the A3, the C-Class Sedan has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver's seat, steering wheel position and outside mirror angle and the front passenger seat also adjusts to the new passenger's preset preferences.

The C-Class Sedan's standard easy entry and exit feature raises the steering wheel and glides the driver's seat back, making it easier for the driver to get in and out. The A3 doesn't offer an easy entry system.

The C-Class Sedan 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 doesn't offer a heads-up display.

The C-Class Sedan's standard Keyless-Go allow you to unlock the doors from any outside door handle, open the trunk, and start the engine, all without removing the key from the pocket or purse. Keyless Engine Start/Stop standard on the A3 only offers hands-free access for the ignition, none to unlock the car.

Consumer Reports rated the C-Class Sedan's headlight performance “Excellent,” a higher rating than the A3's headlights, which were rated “Fair.”

To help drivers avoid possible obstacles, the C-Class Sedan offers optional cornering lights to illuminate around corners when the turn signals are activated. The A3 doesn't offer cornering lights. The C-Class Sedan also offers optional adaptive headlights to illuminate around corners automatically by reading vehicle speed and steering wheel angle.

The C-Class Sedan's sun-visors swivel front-to-side to block glare from the side windows. The A3's visors are fixed into the windshield header.

A power rear sunshade and manual rear side window sunshades are standard in the C-Class Sedan to help block heat and glare for the rear passengers. The A3 doesn't offer a rear or rear side window sunshades.

The Mercedes C-Class Sedan has power folding mirrors that offer unparalleled convenience while maneuvering in tight places or parked. With the mirrors folded it's easier to walk past and help prevent parking damage. The mirrors can be quickly unfolded when the driver is ready to leave. Power folding mirrors costs extra on the A3.

Optional air-conditioned seats in the C-Class Sedan keep the driver and front passenger comfortable and take the sting out of hot seats in Summer. The A3 doesn't offer air-conditioned seats.

On extremely cold winter days, the C-Class Sedan's optional heated steering wheel provides comfort, allowing the driver to steer safely and comfortably before the car heater warms up. The A3 doesn't offer a heated steering wheel.

The Mercedes C-Class Sedan has a standard Homelink wireless remote control system for garage door operation and device management, conveniently located on the rear view mirror. Homelink® eliminates the need for separate garage door openers and associated risks of losing, breaking, or having dead batteries. Audi charges extra for Homelink® on the A3.

Compared to traditional radio, the Mercedes C-Class Sedan's standard SiriusXM satellite radio provides an unmatched listening experience. Its extensive coverage guarantees consistent, crystal-clear reception across the continental U.S., and access to over 100 channels dedicated to a multitude of genres, including music, news, sports, talk shows, and comedy, many with only limited commercial breaks. Satellite radio costs extra on the A3.

To quickly and conveniently keep personal devices charged without cables tangling and wearing out, the Mercedes C-Class has a standard wireless phone charging system (Qi) in the center console. Wireless charging costs extra on the A3.

The C-Class Sedan has a 115-volt a/c outlet on the center console, allowing you to recharge a laptop or run small household appliances without special adapters that can break or get misplaced. The A3 doesn't offer a house-current electrical outlet.

The C-Class Sedan is available in both rear-wheel drive and all-wheel drive configurations. The A3 doesn't offer a two-wheel drive configuration.

The Mercedes C-Class outsold the Audi A3/S3/RS 3 by almost four to one during 2024.