I have driven both normal GTI's and owned an ED30. The only reason the ED30 appealed to me more was because of the 'exclusivity' at the time and the KO4 turbo. In essence there is not a lot of difference between the cars but being able to map it to 300 BHP was a big plus over the normal GTI for me personally.
Looking back at it now the car needs a considerable amount of money spending on it to be able to use the power effectively day to day. Quaife, Coilovers, ARB's and brakes are a must IMO. I had all the engine mods, CAI, TBE exhaust, HPFP and Stage 2+ map, don't get me wrong it is the best car I have owned by a long shot but the power was not really useable below 60
I was having wheelspin at 80mph in adverse weather conditions which was fun for a while but it started to get tiresome
I think coming form yours Rob which is a nicely modified example, you will not notice an awful lot of difference between the ED30 and GTI day to day. To be more specific, you will not be able to use the extra power available...well you can, but your getting to 100+ licence losing territory speed before you notice a massive difference.
Now the R32 is a massively tempting prospect at the moment because of the price like you mentioned and I gotta say I am being tempted by them. I think if I was you personally I would go for the R32, I know you have had a fair few GTI's, if you went for an ED30 you are effectively buying the same car as you currently have, the only big difference is the bigger turbo and strengthened block. If you went for the R32 you would save some money (which you could put towards a turbo fund
) and you would have a completely different car to your last few, 4WD, V6 soundtrack etc etc.
Hope this helps