I don't have anything against MK3/4 calipers - I just don't want to waste money on them and time trying to find them in a scrapyard - when the calipers I have work fine, bar a gummed up handbrake on one side.
Its not inoperable - its just running at 60% of what it should be, I'm sure a little cleanup will free up the mech and get the handbrake working right.
If the hyd. aspect of the caliper wasn't working - I wouldn't bother. But the handbrake mech should be relatively easy to fix.