The CLA'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 CLA and the A3 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, electronic stability systems to prevent skidding, crash mitigating brakes, 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.

There are over 25 percent more Mercedes dealers than there are Audi dealers, which makes it easier should you ever need service under the CLA'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 CLA's 2.0 turbo 4-cylinder hybrid produces 20 more horsepower (221 vs. 201) and 22 lbs.-ft. more torque (258 vs. 236) than the A3's 2.0 turbo 4-cylinder hybrid.

As tested in Motor Trend the Mercedes CLA is faster than the Audi A3:

On the EPA test cycle the CLA gets better mileage than the A3:

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

An eight-speed automatic (SMG) is standard on the Mercedes CLA, 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 CLA's brake rotors are larger than those on the A3:

The CLA stops much shorter than the A3:

For better ride, handling and brake cooling the CLA has standard 18-inch wheels. Smaller 17-inch wheels are standard on the A3. The CLA'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 CLA 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 CLA offers an optional driver-adjustable suspension system. It allows the driver to choose between an extra-supple ride, reducing fatigue on long trips, or a sport setting, which allows maximum control for tricky roads. The A3's suspension doesn't offer adjustable shock absorbers.

The CLA'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 CLA's wheelbase is 3.9 inches longer than on the A3 (107.4 inches vs. 103.5 inches).

For better handling and stability, the track (width between the wheels) on the CLA is 2.8 inches wider in the front and 3.5 inches wider in the rear than on the A3.

The design of the Mercedes CLA amounts to more than styling. The CLA has an aerodynamic coefficient of drag of .27 Cd. That is lower than the A3 (.29) and many sports cars. A more efficient exterior helps keep the interior quieter and helps the CLA get better fuel mileage.

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

The CLA has 1.7 inches more front headroom, .6 inches more front legroom, .3 inches more front shoulder room and 1 inch more rear shoulder room than the A3.

The CLA has a larger trunk than the A3 (11.6 vs. 10.9 cubic feet).

The CLA 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 CLA has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver's seat and outside mirror angle and the front passenger seat also adjusts to the new passenger's preset preferences.

The CLA's standard easy entry and exit feature 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 CLA 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.

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

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

The Mercedes CLA 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.

On extremely cold winter days, the CLA'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.

Compared to traditional radio, the Mercedes CLA'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.

The CLA is available in both front-wheel drive and all-wheel drive configurations. The A3 doesn't offer a two-wheel drive configuration.

The Mercedes CLA outsold the Audi A3/S3/RS 3 by 23% during 2024.