Two significantly similar cars, no doubt about that. Still, each one has something different to offer. Having both cars powered by diesel engines and utilizing the 5-door wagon body style within the same 'Luxury car' segment, the only major difference here really is their wheel drive configuration (rear for the Mercedes Benz and front in the case of the Audi). The first one has a Mercedes Benz-engineered powertrain under the hood, a 4-cylinder, 16-valves 204hp unit, while the other one gets its power and torque from a 4-cylinder, 16-valves 190hp engine designed by Volkswagen.

The fact that the Audi got tested by the European New Car Assessment Programme (Euro NCAP), while the other contender didn't, puts it sky-high safety-wise, in my eyes at least. Still, apart from the official crash test results there are other things we need to be aware of. Both vehicles belong to the luxury car segment, which is generally a very good thing safety-wise, but that fact doesn't break the tie between the two cars. Furthermore, if we'd like to consider vehicle mass in this context too, which we definitely should, CLS offers a marginal difference of 6% more metal.

Manufacturers have been building their reliability reputation for decades now and, generally speaking, it appears that both brands display similar results in faults and breakdowns, when all the models are taken into account. That's the official data, while our visitors describe reliability of Mercedes Benz with an average rating of 4.4, and models under the Audi badge with 4.2 out of 5. Unfortunatelly, I don't have enough insight that would allow me to comment in more details on the specific models level. That apart, owners of different cars powered by the same engine as CLS rank it on average as 4.8, while the one under the competitor's bonnet gets 3.6 out of 5.

Mercedes Benz is a bit more agile, reaching 100km/h in 1 seconds less than its competitor. In addition to that it accelerates all the way to 235 kilometers per hour, 9km/h more than the other car. When it comes to fuel economy things look pretty much the same for both cars, averaging around 4.8 liters of fuel per 100 kilometers (59 mpg), in combined cycle.

Mercedes Benz appears just a bit more reliable, although the difference is truly marginal. The most important thing when deciding between any two vehicles should always be safety, both passive and active. In my opinion, everything taken into account, Audi A6 beats the other contender by far, making it the best choice without even considering other things. From there things take a different direction, with Mercedes Benz offering somewhat better performance, just enough to call it quicker. It does come at a cost though, and that's the fuel consumption... All together, there's not much more to say, in this case I wouldn't even consider anything but Audi. In any case that's my personal view, built upon all the data available to me. What should decide here though is the way you feel about the two vehicles, and I hope you'll find my guidelines useful in the process. Also, you could use the oportunity to find out which car, everything taken into account, would be the perfect choice for you in the eyes of the virtual adviser™, among thousands of similar, yet so different vehicles.