It depends on where you go. If you plan to get into some sketchy places - do the truck camper. The Transit is a tin box with lousy clearance. Even if you get it lifted - clearance will still be an issue and it's a unibody - I just wouldn't trust it for long periods offroad. The Promaster is front-wheel drive - I wouldn't get near anything sketchy with it.The west is the best! Desolate mountains and valleys are ubiquitous (especially in NV)... lots of public land and easy dispersed camping.
A lifted Chevy or Econoline with 4wd - yes. Put a new roof on it and you're sitting pretty.
A 1-ton with a camper may be a little less comfortable but much stouter. You have the money - I would go with that. Nothing the matter with a hardtop = big Northern lite, Bigfoot - sweet trailers.