Class B's cost more in part because you are not putting furniture into a box - it has to fit into a structure with complex curves. Class B's also cost more because they are carefully built with quality materials, unlike most of the junky RV's that are just slapped together to sell for the lowest possible price. For the same reason, used class B's have a higher resale value.
I would second Trekker's suggestion to try renting - Different layouts appeal to different people.
For the question of "best" I suggest that they are all pretty good with the exception of Forester. We had a Sportsmobile for 10 years and 110,000 miles and were quite happy with it. We now have an Advance RV class B and love it. I would suggest visiting the Sportsmobile website (sportsmobile.com) for general information on B's and to see what kinds of layouts are available.