If you drop to 14" you would have to get a bigger tyre profile, so as to not mess up the speedo reading.
I can't see it looking any better with more rubber around smaller alloys...
My Early small bumper GTI has 14" and my big bumper has 15" and I would stick with the 15" TBH...
14" Alloys with Stock 8V suspension...

15" with Eibach springs -40mm on 8v

HTH