If you are addicted to caffeine, Starbucks and small coffee shops while traveling down the highway you need a B to conveniently park at their generally small and tight parking lots. :) If you can do that, that means you have freedom to go almost anywhere on the spur of the moment. A 5th wheeler requires strategy and planning ahead and usually a drive from point A to point B and no real touring.
Almost all the B converters have fixed bed options in their models. They just don't emphasize them much and the dealers never order them on spec. The mattresses are usually hard foam but as retired4fun2002 said, you can always substitute a real custom mattress or just ad a cushioned topper.
