joking aside, i think the 19 inch wheels suit the GTD better than GTi because the silver lines in the front match up with the silver edging on the wheels... whereas the GTi red lines dont and think the 18s are a better fit, especially with the PP bigger brakes fill the 18 inch wheels nicely.
I didnt realise but I checked and the PP front brakes are 340mm v 310 on the non PP car so they are noticeably bigger, as well as having vented not solid rear discs, so its not just about the e diff for all the PP non believers
The one downside, the 19 inch wheels on GTD make the brakes look a bit small..