I have had all 3 sizes on my cupra with 30mm H&R springs fitted
1st 20,s off my mates A4 black edition, to be honest they looked daft to big and made the car look jacked up even though it was lower and they seemed to pull all over the place (tyres were new as well
2nd 19,s looked good, tyres looked like rubber bands The ride was harsh but what do you expect with 35 series tyres, I brought the tyres ready but never got the wheels just kept thinking of them kerbs jumping out on me lol and got a new set of BBS new cheap 18,s
3rd 18,s which I have now with Goodyear f1 as2 ride is just right handles spot on, theres a little bit more tyre on the rim so rides better to me, big plus as well just got 4 new toyo T1 sports to put on lots cheaper than 20,s or 19,s tyres