Both the S5 Sportback and IS have child safety locks to prevent children from opening the rear doors. The S5 Sportback has power child safety locks, allowing the driver to activate and deactivate them from the driver's seat and to know when they're engaged. The IS’ child locks have to be individually engaged at each rear door with a manual switch. The driver can’t know the status of the locks without opening the doors and checking them.
The S5 Sportback’s standard pretensioning seatbelts also sense rear collisions and remove slack from the seatbelts to help protect the occupants from whiplash and other injuries. The IS doesn’t offer a whiplash protection system.
To provide maximum traction and stability on all roads, All-Wheel Drive is standard on the S5 Sportback. But it costs extra on the IS.
Both the S5 Sportback and the IS have standard driver and passenger frontal airbags, front side-impact airbags, driver and front passenger 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, post-collision automatic braking systems, daytime running lights, lane departure warning systems, rearview cameras, available blind spot warning systems, around view monitors and rear cross-path warning.

