I test drove both back to back, with no intention of buying either... for about 3 hours each.
I was always going to order the Golf R, it was just a way of testing a manual v's DSG.
The GTD didn't look quite as good as the GTI because the ride height was slightly higher and the exhausts don't look so good. The GTD did have better looking wheels
The GTI handled a bit better - probably due to its slightly lower stance. Power wise, the GTI had a bit more, but I was surprised by the GTD and how much ooooomph it actually had. People saying a chipped GTD v a GTI would beat a GTI are probably right - but its not a fair comparison as a chipped GTI would beat a chipped GTD!
In my opinion, a diesel car is always a second choice. IF I was doing big miles, I'd feel like I'd HAVE to take a diesel for cost saving. If this was the case, a GTD would be a great choice. I'd always pick a petrol if it was feasible though, as I enjoy revving the t1ts out of it!!
It depends on your circumstances... big miles = GTD, low miles = GTI!
A BW09 car is likely to arrive in March... so I would hang on for what you really want. Whats another few weeks wait?!?!