Not posted here for a long time since I had my mk 6 GTI which I then replaced with a mk6 GTD. anyway I have been getting the itch lately for a return to the petrol models so tested the R and GTI PP back to back.
In short they a both massively impressive cars and I would be happy to own either, I did find with the R though that you really get the feeling that you are piloting a car with huge performance due to the extra noise etc, it just feels special. For me the R has won out and the order has gone in, this decision in part was influenced by the finance deals available with the R which make the ownership costs over 3 years very attractive.
In my example I'm paying the max deposit with the VW pcp and the equivalent spec GTI was coming in at over £100 more than the R. It really makes justifying the GTI difficult in this situation.
For people paying in full then the GTI will make more sense.