Funnily enough, I just looked at an ED30 today.
The ED30 or Pirelli are the ones to go for. Basically an 8P S3 engine in there, which means upto around 350 BHP can be had from relatively simple tuning (exhaust, intake, remap. High Pressure Fuel Pump for maximum 360 BHP or so). Whereas the normal GTI requires the K04 turbo & injectors on top too. APR do a K04 kit for the GTI though, at £2574 including the mapping, should you want to go down that route. But you will still need the HPFP and some K04 injectors on top of that, so probably looking a bit over £3k all in to get the same performance out of a normal GTI, as you would from a stage 2+ ED30. In the end, if your wanting the same sort of power out of a sorted GTI as a sorted ED30, then all in it'll probably cost similar overall. However, the ED30 will be worth more after all said and done.
Of course, that's assuming tuning is of interest to you. Or if you want to even take it that far. As said above, a simple remap on a GTI will be more powerful than a standard ED30, but then again, a simple remap on the ED30 gives you FAR more again.
If not interested in tuning, the ED30 is still the one to go for really. A bit more power, and whilst it will be more expensive to buy, it will be worth more on the other end too. Anniversary Edition Golfs are ALWAYS worth more than regular GTI's. The Pirelli too, because it was so rare.
The Pirelli edition only really exists because ED30 owners were upset that their cars weren't numbered, like the 25th Anni versions were. And so eventually VW stopped making the ED30, and owners could apply for numbered plaques for their cars. Then VW brought out the Pirelli, which was basically an ED30 underneath, but different wheels and trim (I believe), but not numbered. But as it was so close to the end of the mk5's life cycle, there were very few of them made, and are, I believe, even rarer than the ED30. And a bit newer (2008+ usually).
The S3 is also worth a look, but they are at least a couple grand more expensive, often with a more basic spec (although full leather is more popular on them). And, to my eyes at least, not as nice looking as an ED30. Quattro is nice, but then that costs in fuel economy (not that that should really be a consideration with these), and it saps a bit of power (i.e. once moving, the ED30 should be slightly faster, although the quattro will obviously help off the line and such).
The ED30 I was in today had an induction kit, and cat-back Miltek, as well as H&R springs. It wasn't overly noisy, and sounded pretty decent. Gave a decent kick when booted, so was pleasantly surprised by that. I don't think it was remapped, as it was about as quick as my 530d, but it delivered the power / torque in a much nicer manner (obviously). IF I go for it, I will, for sure, be looking for at least a remap on top of existing mods.
