I really have to question whether many people commenting on here have driven the new S4..and if they have, if they drove it hard. I drove the S4 back to back with the F30 335. That torque vectoring rear diff is awesome. Pushed hard around corners the S4 holds the road with more confidence than the 335, yet you can also get the rear end to slide out a bit which gives it a pretty respectable "fun-to-drive" factor. I would not say it is more fun than the 335, but it does not feel like the old S4.
Acceleration in the S4 feels a little faster than the 335, but not much, brakes felt similar under very hard braking, and the transmissions where roughly equivalent (8spd auto vs. DSG) I'm a manual gearbox fan, I didn't get to drive the S4 in manual
I preferred the exhaust note on the 335, as well as the all important steering feel. But to be honest, both of these cars have that slightly artificial feel you get from electro-mechanical steering. I'll take my E92s hyraulic assisted steering over both.
Looks are subjective, so I won't bother commenting other than to say both cars look good and both are comfortable when in the driver seat.
As for pricing, when I built the cars online...with the options I'd want, the 335 was around $53k and the S4 around $56k...those were MSRPs, either way, even if you could get both for closer to invoice you're only looking at $3k difference. Not a lot. Maybe BMWs saving grace is for lease fans, where BMW clearly has more attractive pricing.
Bottom line. These cars are very comparable in price, performance, and features. I'm a BMW fan and would likely lean towards the 335 just due to a slightly
better driving feel, and slightly better looks...but simply put, the S4 outperforms the 335.
To say that the S4 is $10k more than the 335 is just not truly representative of what you'll find when you go shopping for these cars, and to assert that the S4 is just a soulless fwd fancied up A4/Jetta sounds like blind BMW elitism.