It will all come down to how much you want to spend and how much you want to spend on fuel and maintanence.
GTI - be cheaper to get hold of seen as they are made from a 54 plate (I think) and they are a lot more common. Cheaper to run and serive, tax etc than the R32.
ED30 - probably a little more to buy than the GTI at the same age/mileage but noticeable differences in looks and performance. Similar running costs to the GTI.
R32 - probably find one cheaper than the ED30 seen as they were released before but higher running costs and tax band etc. Sound awesome and have the benefit of AWD if you like that sort of thing.
All 3 are fantastic cars at the end of the day so its all down to personal choice. I have driven them all and Id still take the ED30.