I had a Mk7.5 ST3 in Blue for a over 6 years and ended up using it for the occasional track day but mainly my daily.
It had Mountune springs, Short shifter, Stage 2 Collins performance, Stage 1 intercooler, Braided lines, and uprated engine mounts all round. The springs actually improved the ride comfort slightly, as well and handling and stance.
You described it perfectly I think, after a brief test drive I'd agree that the ST is rawer and more fun (especially with the mods) but I want something with more comfort (getting older) and a nicer interior whilst maintaining a great all rounder that the GTI obviously is and really a superior car in general.
I'm actually waiting for the loan to come through as I type and may have the car either end of today, worst case Thursday. Feeling like a child at christmas!
I'll send pics when I can, it's Atlantic Blue with the 19" wheels. Although the 19" look great I Ideally wanted the 18" wheels purely because of the difference in tyre price but they sell so damn quick I had to be less picky!