A VR from a mk3, b3/4 passat, or corrado will require subframes, radiator, transmission, pedal assembly from either a corrado or b3/4 passat, hydraulic clutch system, shifter box, exhaust, Corrado g60 speedo cable or mk3 cluster, wiring harness, and ECU. If the car you're putting it in is CE2 the wiring is mostly plug in play, otherwise you have to break out the wiring diagrams and soldering iron. If you pull a VR out of a mk4 you have all of the above with all of the headaches from the 1.8t you're trying to run from.
With a 1.8t you can keep your current transmission, subframe, and cooling setup. The only mechanical things you have to mess with is the plumbing for intake and exhaust, and a mount for the drive by wire pedal if you go with a later 1.8t. It all depends on if you want to change out all of the mechanics in your car (VR) or modify the wiring in it(1.8t) instead as to which one you want.