Late to the thread
Sorry to be so late here...
BMWs and Audis are both great cars -- choose the right tool for the job.
We had a choice to make recently. We chose Audi for the following reasons.
Requirements -- the car needed to be fun to drive, all weather, comfortable on long trips, occasional track use, four doors for access to the back seat.....
My wife and I are both Track driving Instructors in a broad range of platforms. Both of us have racing experience in a variety of platforms.
What began this insanity (of having a daily driver for occasional track use) was that one day the weather was terribly cold and I decided to take her B6 A4 to the track in completely stock condition. I drove it in the instructor session and was amazed at the balance at speed. Four wheel drive, I expected major push, and was pleasantly surprised. The totally stock brakes and fluid did not last very long and after 15 laps I was using the early toss technique to slow the car. This helped the brakes; but, they were in need of both new pads and fluid after the session.
This experience led me to make the decision that I needed a daily driver to replace the Boxster daily driver (911 track car) which I could still use as an occasional track car. I have track experience in a range of E46 M3. I did all the research and ordered a new (2008) 135I. I am very satisfied with my decision as a daily driver, not so much for occasional track use. The 135's brakes look great; but will not stop the car after between 2 and four laps regardless of what pad I put on and I have tried my favorite pads (Hawk Ht-10). The problem is not the pads or the fluid, it is well documented that the rotor is undersized for the weight and power of the car. Thing two, the car will not turn, it is as far from neutral as some of the worst handling front wheel drive cars I have driven. It is designed to push and ironically, as bad as it is, it turns in better than the 3 series. Turning off the aids to the maximum extent possible cooks the rear brakes in short order. Consider this, I wore out the rear brakes before I wore out the fronts.
I have found the aids to be far more intrusive in the BMW than other new cars I have experience with.
So the time came in August to replace the 2004 A4 with 85,000 miles on it, we looked at a variety of cars. Because of our good fortune with A4s, we purchased a 2013 Audi S4. We recently returned from a 2000 mile road trip and it filled that square as well, surprisingly even better than the A4 which was more comfortable than the 135I. Audi spent some time tuning that exhaust note. Fantastic!! Now I want to get a new exhaust for the 135I.
Despite what it may look like, my only beef with the 135I has to do with its pathetic perfomance on the race track. It seems like it was designed to look good at first glance on paper. A comparison of the brake specs would have helped me; but, why would I expect BMW to put beautiful looking six piston calipers on a 28mm thick rotor (stock rotor thickness on a 1985 Porsche 911 (2700 pounds with 100 less horsepower).
08 135I (AW/Coral Red - delivered 3/15/08 --
13 Audi S4, 83 SC (trackster), 90 C2 (Sally's Carrera), 04 Avalanche Blingmobile