I knew that my post would stir up a hornet's nest on this board
What I will concede is that the decision to go diesel is not based upon practicality today but still is appealing for other reasons. There is no economic reason to choose a used CDI over its used gas counterpart, period. The cars are basically identical otherwise and to argue the CDI is somehow less complex than the gas engine is truly showing one's ignorance of the CDI design. You could say that you might save 10% overall on fuel costs but for the average (15K miles per year) driver that would amount to about $10-$20 a month - hardly something that should come into the equation for buying a Mercedes-Benz.
Add to this argument the present somewhat untested emissions controls of the current diesel models (4 separate systems which all have to work perfectly) and the diesel is easily more finicky and complex that the gas model. This makes the choice of buying a new diesel over a new gasser less of a "no brainer" too.
People think I am some newbie to the diesel world because of my recent posts critical of the practicality of owning one. I learned to drive on a '74 240D in the late 70s and have been an advocate of diesels since then, but today, conditions have changed and unless you are willing to admit that *maybe* the decision to go diesel is impractical you are probably just fooling yourself.
OK, here's my last thoughts on this subject. My reason for continuing to drive a diesel is not because of economy, longevity or ease of maintenance. It is because in the early 1970s when there were gas lines at every station the truck stops always had plenty of diesel. My dad said "there will always be diesel because the military and commerce depends on it - if trucks can't get to the stores the whole economy implodes". That still holds true today. In fact, last summer when the refineries were having their problems meeting demands in the south for gas there was always diesel available. So, I guess I can admit there is one practical reason for owning a diesel powered car - in the event of another gas shortage I think the odds are pretty good that diesel will still be plentiful. That's my reason for owning one - it is the peace of mind of knowing I am not 100% dependent on gasoline. Not the greatest reason in the world but a good one for me.