I actually own both an SUV and a 300D. I often get compliments for the M-B and sometimes get nasty notes left on the SUV because I take up too much space between the lines in a parking lot.
I mainly have the SUV so I can go on long trips comfortably (it also has a working cruise control) and I can carry way more gear and people than the 300D. I also can go longer between fill-ups than the 300D but that's only because the SUV has a bigger tank. The fuel economy is not that much worse on the hwy with the SUV. I get 20 MPG's (Honest!) on the hwy with the SUV and I barely get over 22 MPG's with the 300D. With combined city/hwy driving the SUV's MPG's drop to around 17.5 where as the 300D's MPG's hover around 21.5.
I also need the SUV in the winter when we get snow since it has four-wheel drive. The 300D gets stuck too easily or just plain won't go anywhere in the snow we get.
I can justify owning the SUV.