The one in the driver's screen is faster, it updates routes quickly if you deviate from the route. Sometimes the large screen will take another 15+ seconds to show the same updated route. That's odd enough, but today the driver's screen showed the destination as a left turn, and the large screen showed a right turn. And the spot I was going to was like 200 ft from the street I was on - but they figured it differently (and the large screen was wrong). Weird!