For me, there are several reasons why I tend to think the Golf GTI is a better bet than than the Scirocco:
1. The Golf GTI is built in Germany. The Scirocco is built in Portugal. Nothing against the Portuguese, but the Germans know how to screw a car together better than anyone else.
2. In many ways, the Scirocco is a dumbed-down Golf: no rear hatch opening handle in rear VW badge, extensive use of previous generation Golf and Eos parts, lack of bespoke interior, lack of proper opening sun roof, lack of headroom in the front, and so on. The 'Roc just isn't as sophisticated in my book.
3. Scirocco remains a hatchback whatever you to it, not a focused sports car. So, if you're going to drive a hot hatch, you might as well drive one that offers as much practicality as the Golf: 5-doors, 5 seats, rear leg room, boot space, size of rear hatch opening etc.
4. The Golf is more subtle. It speaks quietly and carries a big stick. It's a bit of a Q car. To me, the 'Roc almost screams 'Boy racer'.
None of this is to say 'Roc is a bad car. It isn't. In fact, it is very desirable. But somehow the Golf is just more complete, more rounded and you get more for your money, even though it is more expensive. Just my 2p's worth!