awesome! I have been driving audis for a few years. I like to see what others are offering. I went and test drove a 335xi bmw and then right after went and drove an s4. To me there was no comparison, the audi was a better car.
Mercs on the other had haven't offered a car with 4 motion that has interested me enough to go down there and drive one. They are owned by chrystler so that can be no good though.
I have always loved audi for the one fact that they think all cars should really have quattro. Even their high end S, RS, exc.
BMW, Merc, and Lexus all think that if you are looking for a sport car, rear wheel is the only option. BMW m3, m5, m6, Lexus is-f, merc c63, have no option to get them with all wheel drive.
actually, mercedes used to own chrysler but they sold them to a private equity group called cerberus last year. To the op, form what i have been hearing and from experience with 4matic cars, audi is more focused on performance and mercedes is more focused on traction in bad weather.