Diesel prices here were always lower than gas until I bought my first diesel pickup What with wear & tear on 6 tires and the cost of diesel it's more economical to drive the van, but if all things were equal I'd take the truck every time.
We've camped in the van, it's only got a drivers seat and a rear bench seat so there's room for either 2 humans who have a close relationship, or me and Pearlygirl there in my avatar. We travel quite a bit to events that require overnight stays, dragging a trailer full of rocks wherever we go, so I'm thinking an aluminum 2-3 horse trailer with modest living quarters would be just the ticket. The truck will pull anything I'd be inclined to put behind it and I think I'd rather go for that setup than a bulky box van. Although a modified Dodge Sprinter diesel could probably be made to work too, and with better fuel economy.