I like the Leon Cupra, but then I have one so I am biased 
. And unlike the MK5 Golf GTi, it is still not common (yet) which is good 
To be fair, the repsonses here are what one would expect from a Golf GTi forum. You would get pro S3 answer from their forum and pro Leon answers from their forum if you asked the same question.
In my opinion, the S3 is a much nicer car than the MK5 Golf GTi. It looks better, it is less common, it has 4 wheel drive and therefore a better basis for tuning (try getting power down fully from standstill on a wet road in an Ed30), the interior is nicer etc etc. Would I have one? No. Why? I need 5 door for the company car policy, but even if I never needed this, the S3 is very expensive - overly expensive in my opinion although it is an awesome car.
Why did I choose the Leon Cupra over the Edition 30? It is rarer, newer, better set up out the box (brakes) and it is cheaper. I also like the way it looks although the centre part of the dash is rank.
However, as it is almost identical under the skin to the Edition 30, what is good for one is good for the other as far as tuning etc goes.
it's not about mechanics, it's about interior and exterior. For me it was worth to pay the premium for E30, actually, I did not even consider Seat as an option.
And its for that exact reason I would not even consider an Ed30 if I wanted an S3 although it also happens to have the 4 wheel drive advantage
