The GLS’ pre-crash front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The MDX doesn’t offer pre-crash pretensioners.
The GLS offers an optional Post Collision Brake, which automatically applies the brakes in the event of a crash to help prevent secondary collisions and prevent further injuries. The MDX 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 provide maximum traction and stability on all roads, All-Wheel Drive is standard on the GLS. But it costs extra on the MDX.
When descending a steep, off-road slope, the GLS’ standard Downhill Speed Regulation allows you to creep down safely. The MDX doesn’t offer Downhill Speed Regulation.
Both the GLS and the MDX 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, 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, driver alert monitors and available lane departure warning systems.
The Mercedes GLS weighs 679 to 1814 pounds more than the Acura MDX. The NHTSA advises that heavier vehicles are much safer in collisions than their significantly lighter counterparts.

