I have a GTI, my friend has an ST.
Obviously this is just my opinion, but overall I definitely think the GTI has the nicer interior. It looks mor luxurous/timeless, the ST is nice as well I agree, but it's loud and boyish. (Which personally, I don't mind, but I can see what people mean that it will look aged and odd after 3-4 years)
Exterior styling is a matter of opinion. I like the way the GTI looks, the ST, looks a little silly to me in terms of hatchback. It's styled like it's trying to say "Look at me!" and it suffers from that stupid small oddly shaped third window on the back like most 4 doors do. I -HATE- those. The GTI has one, but it follows the same curvature as the 2nd one, and looks more like an extension rather than just a quick "Oh shit we forgot the third window in the back, quick quick lets toss one in!". I guess thats where you get the "GTI has a more refined look" thing from haha...My wife thinks my car looks like a retarded car for midgets or something, I can't remember the elegant words she used atm, but when I pointed out an ST, I said well what if I had gotten that, she said she liked it, becuase it looked more like an actual car. I think she's from to Detroit and so she's partial to ford ;p
The ST is definitely faster from the factory, but a stage 1 tune and intake can fix that. The Ricaro seats are very nice, I did enjoy those, but it's something you COULD do in the GTI if you wanted, and the stock plaid cloth seats are nice. So nice that I don't even regret not getting leather, I actually prefer these over leather now haha...seriously I do. I have gotten compliments on them and then people ask where I got them, and I say germany, and they're like WOW cool and I'm like yeah it's where the car is from they came with it from the factory
I hate the wheels on the ST, I like the detroits on the GTI. I mean honestly when I think about it, if I was mysteriously to change cars with my friend, the only things I would feel like I'm gaining over my GTI would be the Seats, the power (which $600 could fix on my GTI), and Ford SYNC (we have a Ford Escape and I like SYNC a lot!). But the stuff I would miss from my GTI would be quite the list...
Friend even said the GTI was his #1 choice just didn't get it because he got such a sweet financing deal with Ford becuase the G/F was buying a truck at the same time with him.