I have a 2008 335xi and test drove a 2012 335i and a 2012 S4. Based on a 30 minute drive on the Audi S4 and a 2 hour drive of the 2012 335i (both automatics) the Audi was faster and more fun to drive and more a pure driver's car. The sport differential is quite amazing on the Audi and allows you to rotate the rear end of the all wheel drive car around corners
I like to hear the engine noise when I am driving hard so a car that is too quiet is a strike against the car for me.
In Canada after discounts, a similar equipped Audi is probably about $3,000 to $5,000 more than the BMW. The rear seat room is also quite a bit tighter in the Audi than the BMW. The Audi will be redesigned in 2 to 3 years while the BMW will be the new style for 5 or 6 more years. I ended up ordering a 2013 335xi because of these 3 reasons.........