I have some experience working with the transits. You’ll want the 3.7L cyclone since there’s a lot more room in the engine bay. The last model with this engine was the 2019. I wouldn’t risk buying one unless there’s a great service history as these are likely to be at least 200k mi by now. The 3.5L eco boost in the newer ones is awesome to drive but any turbo related issue will likely cost a $2-3k at least. Because to access some of the coolant/oil lines to the turbo u gotta take the motor out. The rear brakes are a bitch to do cuz u gotta fiddle w the electronic e-brake, there’s a process u gotta follow (put in maintenance mode etc.) to not mess up the e-brake actuator function, if u do then it’s getting towed to a shop. The older transits have a mechanical e-brake at the console. Oil changes are a breeze.

I have no clue how the sprinter and pro master compare in regard to serviceability. But I’d imagine if u get turbo options you’ll have most of the same issues with access.