To help(?) with the Scudo / Dispatch / Expert (and lately Proace):-
Mk1 199?>2004 ish. Pretty robust and reliable. Nice enough to drive, but only the turbo version. Non turbo was lower geared and awfully noisy at motorway speeds. Only real weak point was cable operated clutch – cable needed replacing every 50k or so. Our only family vehicle for 9 years, 133k all over Europe and saw no reason it wouldn’t have done the same again (until written off by a BMW – also seemed to survive a crash reasonably well….). Owned a Citroen C15 prior to this and always found spares to be cheap and easily available.
Mk2 2004>2007. Slightly facelifted and more refined version of the above. Again only go for turbos, HDI engine with (I think) hydraulic clutch actuation (generally more reliable). If you can find a cheap good one, go for it.
Mk3 2007>2016. Similar-ish chassis / running gear but somehow they made a few things worse on the front suspension (clonking ARB saddle bushes). About 300mm longer at the front (extra crumple zone). Squarer body adds a bit of space. 1.6 HDI is same power as our old Scudo 1.9TD but drives very differently. Very tractable to chug around at the bottom end but nothing extra for hills / overtaking (second half of the accelerator pedal travel does nothing). Keeps up with traffic OK but nothing more. 2.0 6 speed probably a better buy. Have had a few electrical annoyances around the electric windows (switch needed stripping and contacts cleaning, then motor drive stripped – £130 for a full new mechanism).
Leftfield suggestion – could you manage with Berlingo? There is a longer version with extended rear body. The same 90hp 1.6HDI has a different torque / power map that might be nicer to drive (I work in automotive r&d and suspect testing of a fully laden + towing Dispatch probably pooped the old 5 speed gearbox so they tweaked the torque curve).
Mk4 2016> Totally new design, partly based on C4 Grand Picasso floorpan. Have driven one – very nice but probably just going to run our Mk3 Combi into the floor as whole family doing MTB / CX is pretty hard on interiors – no point having a vehicle from new then selling it once depreciation has finished.
Have seen a lot of rotten older Hiaces. Newer ones OK if you are happy with RWD (no problem as a laden work van, but I personally wouldn’t want it running around with just MTB in the back).
Nissan is an interesting size. A friend with back problems had one and struggled with the seats.
Long wheelbase Doblo?