205 Pirelli's vs 2109 ED30's currently registered in the UK.
(
http://www.howmanyleft.co.uk)
A car is only worth what someone is willing to pay for it. The Pirelli is rarer but the ED30 is available slightly older with pretty much the same mechanicals so can make them less desirable. And yes both K04. I think I read somewhere that the Pirelli has a very slightly different fuel system.
Practically the same car although nicer inside!
An ED30 is potentially a cheaper way to get a K04 GTI, but if you want a really good one, be prepaired to pay for it!
Unfortunately we are talking Golf's here. They will depriciate and there is nothing you can do about it. Just enjoy owning it!
I was so slow typing this that 6 people posted hence duplicating BERG's statement.