Handling
The Audi A6 has significantly wider tires than the 3 Series. Keep in mind that bigger tires may look and feel better, while smaller tires could improve gas mileage.
With their similar turning radiuses, the BMW 3 Series and the A6 doubtless handle roughly the same into and out of tight spots.
Drivetrain
The BMW 3 Series's engine is slightly smaller than the A6's, but not terribly so.
The BMW could learn a lesson or two from the Audi A6 when it comes to pickup.
Torque equals pickup, and the Audi A6 will have picked up and gone by the time the BMW 3 Series finally gets moving.
Utility
There's no clear winner between the BMW 3 Series and the Audi regarding transporting cargo.
The Audi A6 and the BMW 3 Series can accommodate the same number of passengers.
Comfort
While the front cabin in the BMW 3 Series offers a bit more head room than the Audi A6, there frankly isn't much of a difference.
The ampler interior dimensions of the Audi make it considerably more spacious for your passengers than the BMW 3 Series.
Dimensions
The Audi A6 is somewhat more ponderous than the BMW 3 Series.
Your wallet will hurt more every time you fill up the Audi A6 than the BMW 3 Series because of its more capacious tank.
The BMW 3 Series and the A6 compete for the same parking spaces.
Cost
The destination charge is a standard charge for transporting the vehicle from its point of origin to the dealer. It costs approximately the same to get the BMW 3 Series to the dealership as the A6.
The BMW 3 Series is quite a bit less costly than the Audi A6 in terms of MSRP.
Overview
The BMW 3 Series and the Audi have the same basic warranty.