Use a passenger van when the regular job is carrying a group that needs designated seats, restraints, and a usable passenger cabin. A cargo van usually makes more sense when the main load is tools, parcels, or equipment and the people aboard fit in its designated seating. Similar exterior dimensions can hide very different interiors.
Count people and baggage together. A van with enough seats may still lack room or weight capacity for everyone's luggage, while a cargo van with an open floor does not automatically provide safe additional seating. The right arrangement must handle the whole trip, including boarding, restraint, storage, and unloading.