The GTI wins hands down every time. Your talking about a modified TDI against a standard GTI, the GTI will remap to 240 which will leave the TDI no matter what stage of tune it is. The DSG box is great, use the search button as there have been loads of threads.
Not to mention the GTI has a better noise, handles better, brakes better etc. Basically the GTI is ready out of the box, whereas the TDI is manufactured with economy and comfort in mind.