I don't recall anyone posting in detail about the relative merits of selling a bike in Shanghai with plates vs without plates. ryanjpyle recently sold one of his MKRide.com bimmers, and sold the bike and plate in separate transactions, so he should have some sense of this.

If you keep the plate, there still will be a procedure for disassociating it from the bike, then reassigning it to your new bike. Not sure which is more mafan.

Guess it depends on whether your buyer wants a plate or not.

cheers