FWIW my opinion is the R is a fantastic car, it’s quick, will eat b roads all day, has plenty of power and sticks to the road like red wine on a cream carpet. If you want something that’s effortlessly fast, a bit understated and great value for money the R is a great car, but I didn’t love it. It felt almost clinical at times, and in order to push it enough to make it really playful, the speeds I was seeing were a good bit the wrong side of legal.
The GTI on the other hand is playful from the get go. It’s not as quick as the R, even in clubsport form, but it feels lighter and more nimble, and you can feel the back start to rotate a little more freely on lift off. Where the R was jaw droppingly quick, the GTI (in the 245 Performance spec at least) made me smile from ear to ear the whole time I was in it. It had proper character, driving it felt almost empathetic. I have an a35 now, and there’s a reason I’m coming back to the GTI fold. I’ve test drive almost every hot hatch (I can’t drive a manual for medical reasons unfortunately) and there are few that feel as special as the golf does to me.
The one caveat, is that it’s all about how you feel. Find a dealer with a used R and GTI you can test drive, and make sure it’s the same rough spec as you’d buy (performance for the diff or standard without) and see how they feel, because it’s purely a personal decision.