Once upon a time, sports fans would not have agonised too long about the choice between a petrol or diesel engine. Yet with the massive advances of recent years in diesel technology, the question has returned with a vengeance. Admittedly, there is a philosophical divide between the GTD and the GTI, not to mention the extra 825 euros that the diesel will set you back. So what's at issue is the pure elasticity of the diesel as against the sheer thrill of revving the petrol version to the max. Or classic versus cult. When performance, consumption and environmental impact are studied objectively, the GTD could still turn out to be the better sports model and therefore the better GTI.