Well, these are two pretty similar cars we have here! It's only details that could potentially make the difference. Considering they both belong to the sports car segment and utilize the same 2-door cabriolet body style and the rear wheel drive system, it all comes up to the specific petrol engine choice they offer. The first one has a BMW-engineered powertrain under the hood, a 4-cylinder, 16-valves 245hp unit, while the other one gets its power and torque from a 4-cylinder, 16-valves 184hp engine designed by Mercedes Benz.

Unfortunatelly, neither of the two vehicles was submitted to the European New Car Assessment Programme (Euro NCAP) testing. This makes it virtually impossible for me to pick one over the other and I'm generally against buying such cars as the safety should really always come first. Still, apart from the official crash test results there are other things we need to be aware of. Both vehicles belong to the sports car segment, which is generally classifying them somewhere in the middle safety-wise, but it doesn't do much to help us decide between the two. Furthermore, taking kerb weight as an important factor into account, BMW Z4 offers a marginal difference of 7% more metal.

Reliability is not the best thing to consider on the make level, but it is worth mentioning 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 with an average rating of 4.2, and models under the Mercedes Benz badge with 4.4 out of 5. Unfortunatelly, I don't have enough insight that would allow me to comment in more details on the specific models level. We should definitely mention that owners of cars with the same powertrain as BMW Z4 rank it on average as 5.0, while the one under the competitor's bonnet gets 4.7 out of 5.

BMW is undoubtly more agile, reaching 100km/h in 1.9 seconds less than its competitor. In addition to that it accelerates all the way to 250 kilometers per hour, 20km/h more than the other car. When it comes to fuel economy the winner has to be BMW Z4, averaging around 6.8 liters of fuel per 100 kilometers (42 mpg), in combined cycle. We can't ignore that 13% difference compared to SLK.

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, BMW Z4 offers slightly better overall protection and takes the lead. It all continues in the same direction, with BMW being considerably quicker, thus putting more smile on driver's face. To make things even better, it consumps less fuel! All together, there's not much more to say, in this case I wouldn't even consider anything but BMW. Anyway, that's the most objective conclusion I could've came up with and it's based solely on the information found on this website. Aspects such as design, practicality, brand value and driving experience are there for you to measure them out. 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.