QuadVan uses an OEM radius arm setup. MG's setup is similar but with some geometry changes to allow a higher lift and bigger tires. QuadVan is locked into a +2 or +4 setup as long as they are converting under Ford's QVM program.
All else being equal, the radius arm setup should ride better, because as the suspension is compressed, the axle makes a slight rear-ward arc. (This is why it's setup with the trailing and level with the axle) The 4-link setup, with the trailing ends higher than the axle ends, causes the axle to move forward under compression, so that adds some resistance to bump-travel.
The benefit of a 4-link setup is it's much easier to adjust caster, IF it was build with adjustable end-links. Also, a properly built 4-link setup with high-qualify rod-ends shouldn't wear out. But the Quigley 4-link, and the factory Ford radius arms (everybody else), utilize rubber bushings which eventually wear.
That all said.... overall bump-travel matters the most, followed by spring rates followed by damping. I'd place the arm/linkage setup behind all those factors, as it pertains to ride quality.
2000 E450 dually V10 wagon