If I understand correctly its simply down to commercials. The NW puts a big injection of cash to the coastline towns its on whereas the UGP is more rural and attracts more of a bike racing crowd in lower numbers. Tricky one to fix. Also they have found a way to give good coverage of the NW200 where I don't think I've every seen similar quality (or even TT quality) for the UGP.

But agree 100% - UGP is the better circuit.