Transit vs. ProMaster?
Another critical issue for any work or play van is cargo volume. Isn't that the main reason to own a van -- to carry stuff in the cargo bay?
When comparing the two choices both of approximately same length and overall height (like just under 20-ft length and 100 inches tall), the ProMaster can carry a lot more volume. I had forgotten the difference in specs until I stood inside the cargo bay and the difference was huge. I'd guess well over 50 cubic feet which in a RV conversion is a lot of additional storage. In a work van that's a lot of extra tools and or supplies.
I'm not sure to what degree this will hurt Transits for personal purchase, but for fleet or mass-produced RVs the smaller interior volume may serve as a significant barrier.
I can't find the revised ProMaster cargo volumes but estimates indicate the PM is much larger than Transit. And if that added space comes at a lower cost it makes a strong argument. Transit is RWD, newer, and probably higher quality, but in a comparison it isn't all one-sided.