I've actually worked at luxury car dealers, I don't find Bentley or Rolls cabin quality to be better than a Mercedes, and I've driven all of them around at least once. Automotive engineering doesn't precisely follow the price curve.
Bentlty and Rolls are covered in a lot more veneer and aesthetics.
They get away with it because they put in monster engines to push their giant hyper-insulated boxes pretty quickly in a straight line and that's about all. The s class is designed to a slightly different specification.
