Honestly they both are probably able platforms. Buses are more common these days. I would bet the bus will likely ride better but is not as customizable. Slightly limited in drivetrain selection compared to the Class 8. I have thought about a bus conversion too but like trucks and never do what the crowd does. Bus might be a little harder to work on the drivetrain. Bus is probably easier to install things like water and sewage systems since they already have the storage compartments installed. Might not be quite as maneuverable. The truck might have a shorter wheelbase. The truck will be more open to unique configurations is probably the only truly significant advantage.
2k PSD 6 speed 4x4 Lariat F-250 dually conversion Alpenlite Durango Camper. 3.73 LS Dana 80.
Pete or KW classic Conventional to haul my racer.