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 Porsche-engineered powertrain under the hood, a 6-cylinder, 24-valves 330hp unit, while the other one gets its power and torque from a 6-cylinder, 24-valves 340hp engine designed by BMW.

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 that fact doesn't break the tie between the two cars. On the other hand, if we'd like to consider vehicle mass in this context too, which we definitely should, BMW Z4 offers a considerable difference of 12% more metal.

I don't like generalizing things when it comes to reliability, although it does seem that BMW does have a slight advantage, at least on all of the models level. That's the official data, while our visitors describe reliability of Porsche with an average rating of 4.0, and models under the BMW badge with 4.1 out of 5. Independent research findings rank Boxster 50% below average, and Z4 37% above the first one. We should definitely mention that owners of cars with the same powertrain as Boxster rank it on average as 3.0 out of 5, exactly the same as the other one.

BMW is a bit more agile, reaching 100km/h in 0.2 seconds less than its competitor. Still, it lacks the power to win the top speed competition, topping at 250 kilometers per hour, 31km/h less than the other car. When it comes to fuel economy things look pretty much the same for both cars, averaging around 9 liters of fuel per 100 kilometers (31 mpg), in combined cycle.

BMW is apparently more reliable, not too much, but just enough. 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 significantly better overall protection, taking the lead here. From there things take a different direction, with Porsche being considerably quicker, thus putting more smile on driver's face. Fuel consumption is more or less the same. It's really tough to make a final decision here, but if I'd need to, I'd say BMW. 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 more than 12.000 different ones in our database.