I'm a die hard Audi fan and loved my S3's. I've driven both pre and facelift RS3 and they are amazing, but I still feel it's all about the engine.
Now, if VW roll out an uber Golf with the 2.5 lump I'll be all over it like a horrific rash. I'm currently in the facelift Golf GTI and I am still overwhelmed at the build quality and standard spec. Alright, it's the GTI model, but standard spec and in my eyes, value for money, it's miles ahead of the equivalent Audi.
For the same spec options which are standard on the GTI, I priced up a 2.0T A3 and the options were near £3.5k extra. I don't have leather, just the Mk1 throw back tartan seats. And they're freakin' awesome.
Bearing in mind the R is the direct competition for the S3, VW currently do not have a RS3 equivalent car. A R400 or R420, 2.5 or huge boost 2.0T, I'd certainly be going to VW as opposed to Audi.
I didn't like the tartan seats when I had a look at one, prefer the standard heated leather seats on the S3. Personally I had the choice between the R and S3 and thought the better interior, MMI/virtual cockpit software and residuals (based on what we saw with the PFL R and S3) of the S3 made it the better choice. The Golf R has a better steering feel though. The real choice was between the S3 and GTI Clubsport and I wish I test drove the clubsport before I bought the S3 even though it has the PFL interior and tech. A possible Golf R400 would only interest me if it was like the Clubsport in terms of exterior/interior styling and a special edition like feel.