A passenger van is a type of vehicle; a fleet vehicle is a vehicle operated as part of an organization's managed transport resources. The categories overlap. A hotel's passenger shuttle can be both a passenger van and a fleet vehicle, while the same hotel's maintenance pickup is a fleet vehicle with a different job.
That distinction changes what to compare. Passenger-van questions concern seating, access, luggage, and the trip. Fleet questions concern who assigns the vehicle, maintains it, authorizes drivers, records use, and provides a replacement when it is unavailable. Choosing a van and managing a fleet are connected decisions, rather than competing body styles.