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 4-door sedan body style within the same 'Large family car' segment, the only major difference here really is their wheel drive configuration (rear for the BMW and 4 x 4 in the case of the Audi). The first one has a BMW-engineered powertrain under the hood, a 6-cylinder, 24-valves 258hp unit, while the other one gets its power and torque from a 6-cylinder, 24-valves 272hp engine designed by Audi.

The first thing to look into here would be the results from European New Car Assessment Programme (Euro NCAP) tests performed on the two cars. Good thing is that both vehicles got tested, with the same number of safety stars gained in the process. Still, apart from the official crash test results there are other things we need to be aware of. Both vehicles belong to the large family car segment, which is generally a good thing safety-wise, but it doesn't do much to help us decide between the two. On the other hand, taking kerb weight as an important factor into account, Audi A4 offers a considerable difference of 13% 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. These are the official statistics, while our visitors describe reliability of BMW, as well as Audi, with the same average rating of 4.2 out of 5. Some independent research have also placed 3 Series as average reliability-wise, and A4 is more or less at the same level.We should definitely mention that owners of cars with the same powertrain as 3 Series rank it on average as 4.8, while the one under the competitor's bonnet gets 5.0 out of 5.

Audi is a bit more agile, reaching 100km/h in 0.3 seconds less than its competitor. Still, it lacks the power to win the top speed competition, topping at 249 kilometers per hour, 1km/h less than the other car. When it comes to fuel economy things look pretty much the same for both cars, averaging around 5.1 liters of fuel per 100 kilometers (55 mpg), in combined cycle.

BMW 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 A4 offers significantly better overall protection, taking the lead here. It all continues in the same direction, with Audi offering somewhat better performance, just enough to call it quicker. It does come at a cost though, and that's the fuel consumption... It's really tough to make a final decision here, but if I'd need to, I'd say 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. In case you have two minutes to spare I invite you to define your needs, desires and budget and see which car would be chosen by the virtual adviser™, among thousands of similar, yet so different vehicles.