Look at the number of TD cars on the right hand lane in our motorway, you sort of get the idea that most turbo diesel driver think their car got some supernatural acceleration over their petrol equivalent. This sunday when I took my 997C2S out for a spin, I was tailgated by a Vauxhall Insignia with a diesel badge proudly display at the rear end. (I let him past)
Used to see this argument over a few BMW forum as well---335i vs 335d
Let's compare the GTD and GTI assuming their gear ratio is similar
Higher power to weight ratio will always gives you better outright acceleration. Higher bhp, rev range and low drag will gives your petrol car a higher top speed. That's why your Gti can accelerate from 0 to 100mph under 16.5s and top out at 149mph. The 30-70mph thru the gears is very good--5.8seconds! The GTD will get slaughtered at Santa Plod or any cross country B-road race.
However, on normal roads, the only chance we can show off our car overtaking ability is overtaking a lorry who is travelling at 50mph. I bet the difference between the two is minimal. On a decent straight less than a qarter mile, I doubted a GTI will pull out any significant advantage over the GTD. If you look at the in-gear acceleration between a GTI and GTD in third 30-50mph, both cars can complete this in very similar time!
I think turbo diesel is a perfect way to get from A to B but I find the narrow rev range is a bit of a anticlimax! It also tends to weigh more than their petrol equivalent which means more understeer in a front drive car!
In my experience, a good driver with trackday experience is better than adding 50bhp to your car. One of my mate is an ex-rally driver. He drove round the Beford Autodrome circuit in his Cayman S quicker than some newbies in their 997 turbo. I can't get anywhere near him when we did a Cat and Fiddle run a few months back!