Who makes a Quality B+ Mercedes Sprinter Coach?

Winnebago is the only one one the list that builds B, B+ motorhomes. The rest of the manufactures you listed build Cs.

The best of the bunch is Leisure Travel Vans followed Winnebago. The rest are so-so.

You may think Tiffin's are good because of their Class A coaches, but the Wayfarer has a ways to go. Primarily it is plagued by being grossly overweight for a Sprinter. Very low OCCCs in every floorplan. May want to give them a few years to figure it out.