Surely it depends what model, engine and trim level you go for?
Plus there are different aspects to "luxury" - engine refinement, feel of the controls, general internal build quality, reliability, longevity. You could even extend it to safety in the broadest sense of the term "luxury", as sitting at home in one piece is more luxurious than a stay in hospital with broken bones, or at worse being 6 feet under.
Audi and Mercedes both make some great cars.