Is it only available as a TSI???
Are you referring to VW's Twin charged offering seen in the 1.4l engine?
TSI is used on MK6 GTI and the MK7 will use TSI as well with the 2.0l single blower setup.
VW did confuse things a little when they changed from TFSI to TSI in the MK6 GTI.
I saw a MK7 in a stealership and it was ok...the GTI will look better.
As for the A3/S3:
http://www.audi.co.uk/new-cars/a3/s3.html I think that looks soft,fat and round nowt sharp about it at all. The front of the car is too short, bonnet looks squashed with a lardy rear.
In comparison the MK7 GTI looks better but they will no doubt share features so juries out I guess.