Advantages of a Sprinter:
They hold their resale value.
The Mercedes logo.
They are the top dog when it comes to MPG.
They are reliable.
Disadvantages:
Finding service on a Sprinter chassis rig may be problematic.
There is a cost premium around $15-20k over a Ford, and that cash can buy a lot of gasoline.
If you are looking to downsize, and don't mind waiting a year or two, Ford is putting out their new chassis offering next year, and Dodge is putting out a cab chassis which is very class C friendly (www.fiatcamper.com) later this year.
Both the Ford and the Fiat *cough* Dodge will be very good chassis offerings, and will have MPG comparable to the Sprinter, but will also have gasoline models available.