The Tiger is completely different from a truck bed camper -- replace the pickup box and you get a lot more interior space. It's more like a class B+, or a mini-class C. If the RV keeps the stock van walls (like a Sportsmobile or the GMC one Hutch is considering), I think the drop-in pickup campers have more usable space. Biggest advantage of the van over the truck is the ability to walk through from the RV space to the front; some vans use a swivel front passenger seat so you can use that seat "backwards" in RV arrangement.
Every RV style has its pros and cons; there is no one perfect arrangement.
Those Tiger RVs are pretty sweet, esp. with an extended cab (more passenger seating). Not cheap though.