X3 on the Transit. The EcoBoost + 10 Speed is by far the best powertrain combo available for any van.
The Sprinter does have some issues with diesel emissions, as do all the automakers (the big ones are mostly figured out, but the small ones from all the OEMs regularly have issues still). But the bigger deal is sparse repair center coverage.
The AWD in the Transit can transfer 100% torque to either axle, where the MB system has a 1/3-2/3 F-R torque split. Van Compass has a 2" lift available.
But for trails, true 4x4 on the Transit is even better, in which case I'd recommend the Transit system. Quigley's are more readily available, but the QuadVan setup uses more stock Ford wear parts, and less custom stuff, so repairability in the future should be easier.
The new 2020 Transit has a factory seat swivel option, and also a push-down-parking-brake option so adding an aftermarket swivel won't require the seat-lift anymore.
The Ram ProMaster isn't really in the same league. It's Front Wheel drive only, with a transverse V6.
2000 E450 dually V10 wagon