The advantage to an electric fan is that at idle , they move more air than an engine driven fan simply b/c they have FULL RPM at idle, an engine fan does not b/c it's speed is engine rpm dependant. That is why Benz uses aux electric fans for both coolant temps and a/c high side pressure aids...it is at idle/stand-still that these fans do their job of keeping both temps and pressures in check b/c engine fans have an airflow volume problem at those low rpm/idle conditions.
When a care is traveling, you have airflow from vehicle speed and these electric fans are not even needed.