My mom recently traded her CLS550 4Matic for an A6 3.0. Had lots of electronic problems with the Mercedes. Gorgeous car, drove well, but the problems just mounted and mounted. The GPS stopped working. The rearview camera stopped working. And there was other stuff too. The A6 is perfect for her. Easier to see out of, easier to get in and out of, more comfortable, more practical, better AWD system.
I owned two Audi's, both A4's, and they were great cars for me.