Iny summed it up pretty well.
I'll add;
you get more bang for the buck with a slide-in
also, a well maintained TM will out last a van.
With slide-in, it's a piece of cake to move to a shinny new van.
It's large dollars and bigger headaches to move a direct drive into a new van.
So, when your van gets tired and becomes a money pit in repairs, or starts to "ugly out", you'll spending good money after bad to do major repairs and body work on a tired war wagon
another thing, vehicles aren't made to go 50 MPH sitting a driveway.
Guys talk about how reliable
DDs are, but never mention the repairs to the van that aren't common for non DD.
Like water pumps, fried/brittle wiring harnesses, computers cooking and other engine compartment heat related failures.
..L.T.A.