As you know Chris, when I changed my 2013 GTD earlier this year, I'd actually ordered a GTI. Don't get me wrong, despite what the diesel haters on here will have you believe (

) it's a superb package, great economy for the performance on offer, not really
that much slower in the real world than a GTI (except the traffic light grand prix), but I think the best looking of the performance Golf's (no red accents on the lights and interior), and a better front end than the R (personal opinion before all you R owners shoot me) - but then you know all this as you had one.
No I wanted a GTI as I'd had 3 diesels on the row and whilst all brilliant, there's just something about a performance petrol engine experience that the diesel doesn't offer (I'm not talking about performance, but rather the feeling it gives you). As it happened, my job changed slightly which means around 20-25k miles per year rather than the 7-8k miles I was doing, so in the end, I opted or a new 2016 GTD. TBH, I'm delighted with it as it's 10% better all round than my 2013 model. To give you an idea, I haven't been traveling much at all really and just from work to home and back, due to losing my father in law, then my mother within weeks recently. For my pottering to work and back though usual town traffic etc, with little motorway work, I've averaged 47.1 and 48.6 over the last two tanks. When I took the new car down to Swansea in May 2 weeks after getting it (with only 300 miles on it), I averaged 60.3 overall for the 465 mile round trip (calculated with brim to brim fill) - and that's DSG as well.
I still think if my mileage was as small as yours is I'd be running a GTI as the fuel saving over a GTD wouldn't be too bad. As for the "R", well yes, technically it's the best of the bunch, the fastest, best handling etc (and with some unique colors), but I don't think they look as nice as the GTI/GTD, and around my parts are as common as muck. In terms of frequency, near me, it's R then GTD then only a few GTI's, so that makes the GTI quite exclusive and another good reason to own one.