Nothing wrong with skinny tires! (185-14)

Less rolling and aerodynamic resistance and tire weight
means (probably mostly theoretically) better mpg.

Better traction in rain and snow and (not bottomless) mud
because of less aquaplaning (flotation) due to greater psi
on the road.

Less expensive.

205 load capacity is a little greater but do you need it?
Synchro is heavier vehicle and 205s recover potentially lost
load capacity--wouldn't have looked good to have to
advertise less load capacity.  Greater dry-road cornering
(lateral g) capability and greater resistance to
acceleration wheelspin are not relevant to Vanagon.

5.5-in rim is minimum for 205.