This is often discussed. Technically a class B+ is a "C", so this post likely will wind up in the "C" forum eventually.
Pros of a Sprinter:
MPG.
Good suspension.
No doghouse.
Keeps its horsepower when in the mountains.
Cons of a Sprinter:
Mercedes prices when it comes to repairs.
Finding service bays can be tough. Sprinters are too big for a lot of M-B dealers, too small for the Freightliner depots.
Higher initial cost of chassis.
Pros of the Ford chassis:
Less initial money.
Tried and true, pretty much unchanged except to shake the bugs out.
Fixable almost anywhere.
You usually will get a gasoline generator, which means more run time in general.
Cons:
More fuel used.