Tough call. I drove the current model S3 just before the 135 came out and thought it was great. I was just about to put my money down when the 135 coupe was launched so I thought I'd better go test drive it.
135 is in my garage, which pretty much sums up the winner IMO. S3 is a good car, I just loved the 135 at first sight and was it's slave after first drive.