I cross-shopped the 2015 models of Audi S3, Mustang GT, and M235i, and test drove all of them before choosing the BMW.
I liked a lot of things about the S3. The one I drove had the Daytona Grey package with red leather seat inserts and interior accents. The interior was amazing. The gauges and electronics were also amazing - much better than the M235i dash, IMO. I even liked the exterior styling a bit more than the BMW truth be told.
Driving the car, it was very responsive to both steering and throttle inputs, and stuck like glue everywhere.
The deal-breaker: no manual gearbox.