Part of that is down to the tyres. I don't know if you have much experience of driving on track, but the cup tyres change their behaviour with heat in them, they have a "window" as it were, where they offer an enhanced performance. before deteriorating.
That is mostly pointless on the road, as Volkswizard didn't seem too upset the factory car came with more road focussed Pirelli.
One of the biggest thing you notice between CS & CS-S compared to the regular GTi is the effect of the larger turbo.
The larger turbo engines rev more freely in the upper rev range, where as you feel the regular GTi has given it's best in the mid range.
Yes it is the same turbo in the CS/ CS-S as the R, but the lighter cars feel like they pick up better. That is comparing manual gearboxes, the dsg have their own characteristics to add to the mix.