if you can live with the fact you didnt buy an ED30 then
Consider the resale too , ED30 although oversold should still hold its value better than a GTI
Depends how much cash you have , but I could argue that the price differential may allow you to buy an LSD.
Full house mods on both = ED30 faster
mid mods on ED30 , full house on GTI = GTI wins
as stated ED30 has more 'headroom' but you need various upgrades to be able to utilise the full hp.
Drive both , you may prefer the total lagless GTI. Although it may have more hp it doesnt make you faster...
If youve got the money its ED30 + LSD + suspension = woohooo