That may be true, but the E500 wagon has a much more appealing look for the interior and exterior. Also, the E500 gets a higher mpg than the cummins and is more energy efficient. The cummins is load and obnoxiously load and pollutes the air. The E500 wagon rides much smoother than the cummins.
It may be true that Mercede's quality is superior to Ram's, but the cummins engine is more energy efieceint, it produces more energy per gallon of fuel used. That being said it does have worse fuel economy, around 16 MPG. The newer 6.7 liter Cummins engines are more refined than the 5.9 liter one so they are quiet. Also, the modern Cummins are clean, they use diesel exhaust fluid to reduce emmisions of green house gases.