I personally went for a GTI over an Ed 35. There are things I like about both.
First, the Ed 35 can be remapped via OBD port (AFAIK) where as the later GTI's can't, the ECU has to be opened for them to be mapped. That's not put me off a remap but I'm sure it will put many off.
The GTI has a newer engine, and hence less tax, better economy, and alongside slightly less power, cheaper insurance (which is quite important for me given my age). The Ed35 has the same lump from the S3, R etc but detuned a bit. I think it will map to around 300 bhp. The GTI engine "should" be more refined. I can't comment as I haven't really driven the S3/R/35 engine, at least not for a few years. There's very little in them 0-60.
The Ed 35 has darker tints, darker lights (they are tinted) and some fancy side skirts and door sills. I'm personally not fussed about any of them. The side skirts are nice BUT I quite like the black GTI skirts and they certainly don't look rubbish, which is what I was worried about so I considered fitting 35/bluemotion/R skirts afterwards. I will no longer bother doing this.
I personally don't like the Ed35 wheels and I love the Monza Shadows which is another reason I went for the GTI. Yeah the Monzas are common as muck on the GTI's but that's because they look good!
It's a difficult decision, but the wheels + newer engine made me go for the GTI. Residuals will probably be better on the Ed35 but that remains to be seen. Maybe people will pay more for economy ? I'd be interested to know what balloon VW quote on a similar spec GTI vs 35.
Either way, I don't think you will be disappointed.