Here's my comments regarding a Class B+ or Class C RV built on a Sprinter chassis:
1. Coach walls and steps are too low to the ground - how you gonna take them reliably off paved roads?
2. Too tall for their dually track-width in the rear - they look unstable side-to-side.
3. Difficult to find emergency servicing when something goes wrong a long way from home.
4. They're not basement-design motorhomes - where's the several smaller outside storage cabinets that are actually tall enough to fit much into (in addition to the single main one that they all have)?
5. I don't think that the double coach batteries are right under the doorstep - accessible from the outside or inside, rain or shine ... and kept a bit warm from being located just under the floor of the coach in cold weather. (Warm batteries perform better in the winter - which is when you need them most to perform up to their full potential.)
6. If you want one with a stronger coach structure you must get one without slides. But without slides, they are just too narrow to get around in.
7. The commonly available Ford E450 and Chevy 4500 chassis under a motorhome means you can pretty much carry anything you want in them if you have one of those two chassis under a Class B+ or Class C motorhome up to around 28 feet long.
8. Diesel is available in whole lot of places but not "everywhere". Gasoline is available in just about every little podunk U.S. town.
9. Not a lot of the Sprinter based rigs have a full cabover sleeper bed. You may have to search hard for a cabover bed one that also has the other features you might want.
10. It unfortunately may not be recommeded to idle the Sprinter engine an hour or two in order to take advantage of it's large alternator in order to quietly and quickly charge the coach battery bank in noise sensitive drycamping situations where solar won't do it and where the built-in generator may be too load. This idling limitation does not exist, for instance, with the Ford V10.
11. For what it's worth speaking from experience, the Ford V10 pulling our small Class C has continued to pull strong so far up to and through a 11,300 foot pass in Colorado.