Cargo vans usually come bare from the driver compartment back, making them a good blank slate for modifications. Passenger vans have seats and seatbelts and stuff that need to be removed first.
Cargo vans have fewer (if any) windows in back, providing privacy and making it easier to insulate the walls. Passenger vans have windows in back, making it easy to see around you when you drive and allowing more light in so you don’t feel as confined, But the windows need to be covered with something for privacy. They also need to be insulated, because all that aforementioned sunlight can turn the van into a solar oven in summer and let all the heat out in winter.
Depending upon the state, cargo vans might need to be registered and insured as commercial vehicles, which is more expensive. Passenger vans are treated like big station wagons.
Cargo vans tend to tell thieves, “There are probably tools and other stuff in here worth stealing.” Passenger vans tend to say, “There’s a lot of seats, dog hair and dried kid vomit in here.”
Cargo vans usually cost more on the used market because there’s always a demand for them among various tradespeople. The demand for used passenger vans is lower, so the prices tend to be lower. Fewer people have the need or desire to haul a dozen people from place to place.
Considering these pros and cons, I’m more open to the idea of a passenger van when and if it’s time to replace the Rolling Steel Tent.
Oh, but there’s one more thing. See in the photo below how the air vents hang down from the roof, and how there’s a big duct running down the left side? Those take up precious headroom. And there’s probably an auxiliary A/C gizmo in the back corner. That’s a pain in the butt to remove. So maybe not a passenger van after all.