Well, I did the maths on annual running costs using the stated combined mileage. On 10,000 miles a year, which I rarely do (7,000 on average), taking into account lower tax and everything, the savings were about £400 a year at current rates and my insurance costs. OK, so that's a decent chunk of money, but it's not when you consider what you are losing in part-exchange and depreciation by getting the car in the first place.
Now, for a company car owner, the GTD is a more practical choice because the tax will be a lot lower. For a private buyer, I just don't see the logic. If a private buyer can afford to trade up to a car as expensive as the GTD, then surely they can afford to run a GTI?! I actually considered it due to the lower monthly payments, but I knew that I'd regret it, because what I really want is the GTI for its looks, its smooth power delivery and nimble handling.
I went with my heart, like it did last time, and I know I have made the right decision. For me, the GTI is refined enough to be an everyday car already. It's not about racing at the lights, or how fast you can overtake on the motorway. For me it's about having a connection with my car, and that's something I wouldn't get with the GTD, because I knew it's trying to be a GTI, but not quite getting there. For that same reason, I get why people like the GTD.
I plan on keeping mine for several years too, which is why I come back to depreciation. Once the 3 years are up and you own the car, suddenly you have all that spare money each month. After which, two monthly payments more than covers the increased annual running costs of the GTI over the GTD.