At the time of wanting to order my GTD, there was no viable alternative for me. My Scirocco had been very practical for a 3 door coupe, as much as I liked the TT, only having one car in the household, it needed to be reasonably practical, and I knew the MK2 TT was on its way out anyway. GFV was important for me too, it would be hard for me to shell out for a car with massive depreciation no matter how good it drives. I also think that the best drives are behind us now - electronically adjusted everything in very up to date cars dulls the drivability somewhat and there is very little in the way of thrills to be had doing legal speeds - sturdy new cars are so sterile these days.
As a semi-fuel miser (I can put up with poor/average diesel economy to put my foot down and have some fun, rather than drive like a nun to glean an extra 5mpg), it was always going to be diesel.
When I got my GTD I was impressed with every aspect of the car but the performance, it seemed no faster than my Scirocco 170TDI, and those sh!tty Bridgestones - what a crime. VW created an athlete and then shot him in the knee when they shod my car with those abysmal tyres.
Performance disappointments have been overcome with the DTUK box. If I hadn't taken the plunge with that, my car would probably still be a mild disappointment on a daily basis on that score (although initial grip with my tyres is an issue i'll live with because i'm too tight to spend £240 on a set of fronts to replace unworn Bridgestones)

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My next car will probably be an S3, or maybe a MK3 TTS. I think there is no middle ground for me and mpg, either i'll get 50mpg and have decent performance or i'll say "to hell with mpg" and be looking for significantly more than a GTI can give for just a little more thirst than the GTI.