Compare the2023 BMW Z4VS 2023 Porsche 911

The Z4’s pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The 911 doesn’t offer pre-crash pretensioners.

The BMW Z4 has standard driver and front passenger side knee airbags mounted low on the dashboard. These airbags helps prevent the driver and front passenger from sliding under their seatbelts or the main frontal airbags; this keeps them better positioned during a collision for maximum protection. Knee airbags also help keep the legs from striking the dashboard, preventing knee and leg injuries in the case of a serious frontal collision. The 911 doesn’t offer knee airbags.

The Z4 has standard Post-Crash Braking, which automatically apply the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The 911 doesn’t offer a post collision braking system: in the event of a collision that triggers the airbags, more collisions are possible without the protection of airbags that may have already deployed.

To help make backing out of a parking space safer, the Z4’s optional Cross Traffic Warning uses sensors in the rear to alert the driver to vehicles approaching from the side, helping the driver avoid collisions. The 911 doesn’t offer a rear cross-path warning system.

The Z4’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 911 doesn’t offer a driver alert monitor.

Both the Z4 and the 911 have standard driver and passenger frontal airbags, front side-impact airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control, electronic stability systems to prevent skidding, daytime running lights, rearview cameras, available lane departure warning systems, blind spot warning systems and rear parking sensors.

BMW pays for scheduled maintenance on the Z4 for 2 years and 26000 miles longer than Porsche pays for maintenance for the 911 (3/36,000 vs. 1/10,000).

There are over 80 percent more BMW dealers than there are Porsche dealers, which makes it much easier should you ever need service under the Z4’s warranty.

J.D. Power and Associates’ 2022 Initial Quality Study of new car owners surveyed provide the statistics that show that BMW vehicles are better in initial quality than Porsche vehicles. J.D. Power ranks BMW above average in initial quality. With 35 more problems per 100 vehicles, Porsche is rated below average.

On the EPA test cycle the Z4 gets better mileage than the 911 Cabriolet:

Regenerative brakes improve the Z4’s fuel efficiency by converting inertia back into energy instead of wasting it. The 911 doesn’t offer a regenerative braking system.

In its Green Vehicle Guide, the U.S. Environmental Protection Agency (EPA) rates the BMW Z4 higher (5 to 7 out of 10) than the Porsche 911 (3 to 5). This means the Z4 produces up to 24.5 pounds less smog-producing pollutants than the 911 every 15,000 miles.

For better handling and stability, the average track (width between the wheels) on the Z4 is .6 inches wider in the front and 1.4 inches wider in the rear than the average track on the 911.

The Z4’s front to rear weight distribution is more even (51.2% to 48.8%) than the 911’s (39.5% to 60.5%). This gives the Z4 more stable handling and braking.

The Z4 is 7.2 inches shorter than the 911, making the Z4 easier to handle, maneuver and park in tight spaces.

The design of the BMW Z4 amounts to more than styling. The Z4 offers aerodynamic coefficients of drag from .29 to .31 Cd (depending on bodystyle and options). That is lower than the 911 (.31 to .33) and many sports cars. A more efficient exterior helps keep the interior quieter and helps the Z4 get better fuel mileage.

The Z4 has 1 inch more front headroom and 1.7 inches more front shoulder room than the 911.

The Z4 has a much larger trunk with its top down than the 911 Cabriolet with its top down (9.9 vs. 4.6 cubic feet).

With its convertible body style, valet key and remote trunk release lockout, the Z4 offers cargo security. The 911’s non-lockable folding seat defeats cargo security.

The Z4 offers a 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 911 doesn’t offer a remote starting system.

Unlike the driver-only memory system optional at extra cost in the 911, the Z4 has standard driver and passenger memory, so that when drivers switch, the memory setting adjusts the driver’s seat, outside mirror angle, climate settings and radio stations and the front passenger seat also adjusts to the new passenger’s preset preferences.

The Z4 offers an optional heads-up display that projects speed, tachometer, warning 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 911 doesn’t offer a heads-up display.

If the windows are left open on the Z4 the driver can close them all from a distance using the remote. On a hot day the driver can also lower the windows the same way. The driver of the 911 can only operate the windows from inside the vehicle, with the ignition on.

In case of a sudden change of weather, the Z4 offers an optional remote convertible top that can be raised from a distance to protect the interior of the vehicle from damage. On a hot day the Z4 offers an optional remote opening feature, to lower the top from outside. The 911 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.

To quickly and conveniently keep personal devices charged without cables tangling and wearing out, the BMW Z4 offers an optional wireless phone charging system (Qi) in the center console. The 911 doesn’t offer wireless personal charging.

Insurance will cost less for the Z4 owner. The Complete Car Cost Guide estimates that insurance for the Z4 will cost $5805 to $14240 less than the 911 over a five-year period.

IntelliChoice estimates that five-year ownership costs (depreciation, financing, insurance, fuel, fees, repairs and maintenance) for the BMW Z4 will be $38201 to $103140 less than for the Porsche 911.

Consumer Reports® recommends the BMW Z4, based on reliability, safety and performance.