I've owned a mk5 GTi, FR1.8 tsi and FR2.0tsi. Not the ST though.
The 1.8 feels and sounds (although via a soundaktor) more like the GTi than the 2.0tsi does. It revs more freely higher up the rev range, whereas the 2.0tsi feels (and sounds) 'diesel-esk', with a lot more torque low & mid range...