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 325hp unit, while the other one gets its power and torque from a 6-cylinder, 24-valves 343hp engine designed by BMW.

The fact that the BMW got tested by the European New Car Assessment Programme (Euro NCAP), while the other contender didn't, offers a slight advantage, as the 4-star rating is better than none. Moving further on, let's take a closer look at some additional safety-related facts. 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, if we'd like to consider vehicle mass in this context too, which we definitely should, 911 offers a considerable difference of 10% more metal.

Manufacturers have been building their reliability reputation for decades now and, generally speaking, it appears 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 3.9, and models under the BMW badge with 4.1 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 911 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, 35km/h less than the other car. When it comes to fuel economy the winner has to be 911, averaging around 11 liters of fuel per 100 kilometers (26 mpg), in combined cycle. We can't ignore that 10% difference compared to BMW Z4.

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 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. To make things even better, it consumps less fuel! It's not difficult to say then that if I'd need to make a choice, it would definitely be the Porsche. Nevertheless, let's not forget that people have different preferences and needs, so what really counts is your personal feel. I'm only here to help. 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.