Having owned 5 SEAT Ibiza Cupra's in total over the last 5 years, the interior is terrible in comparison to any VW.
That is, as mentioned before, evident in teeth rattling ride quality, overly hard suspension and a basic interior quality.
However, engine wise, they always impressed me, OK they are VW/Audi parts anyway, but they were great cars.
If the LEON had the same quality of interior as the Golf GTi then I'd have been tempted, as it's less common, and quite a nice looking car, but it is leaps apart in quality and until SEAT improve that side of their cars, i'll stick with VW.
To me, the greatest SEAT car, was the Ibiza Cupra MK3.
...Get yourself a later (2009) 5 door ED30 or Pirelli!