Overview

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 6-cylinder, 24-valves 265hp engine designed by Porsche.

Safety

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. That aside, let's consider some other aspects which affect safety. 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. Furthermore, taking kerb weight as an important factor into account, BMW Z4 offers a marginal difference of 3% more metal.

Reliability

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 BMW with an average rating of 4.1, and models under the Porsche badge with 4.0 out of 5. Some independent research have also placed Z4 13% below average, and Boxster 37% below the first one. That apart, owners of different cars powered by the same engine as BMW Z4 rank it on average as 5.0, while the one under the competitor's bonnet gets 3.0 out of 5.

Performance & Fuel economy

BMW is a bit more agile, reaching 100km/h in 0.1 seconds less than its competitor. Still, it lacks the power to win the top speed competition, topping at 250 kilometers per hour, 14km/h less 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 24% difference compared to Boxster.

Verdict

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 slightly better overall protection and takes the lead. From there things take a different direction, with Porsche 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 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. 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 more than 12.000 different ones in our database.