I'm with these guys...go drive one and you'll notice the difference. However I can share that I came from a D3 S8 with a V10 into a Panamera 4s and found there to be a night and day difference in the drive of the cars, and I believe the difference is simple.
My Audi (and your MB) are luxury cars first and foremost and the Audi added some performance. The Panamera is a car built on a stretched sports car platform and thus handles much differently and IMO is just a different class of vehicle.
hope that helps...but GO drive one