I test drove S4, E90 M3 and 2008 M5 before ordering E90. All with dct/dsg/smg. While there was a debate in my head between M3 and M5, S4 was clearly out of the picture. Dynamics and transmission in Audi simply can't compare with BMW, at least to my taste. It was funny that even my wife was advocating for M3 over S4 and she is the reason I'm going from 6 speed e46 M3 to four doors dct car...
Now, I think it compares well to 335. A friend of mine had one that I got to drive on occasion and S4 compares to it favorably in may ways.