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 6-cylinder, 24-valves 265hp unit, while the other one gets its power and torque from a 4-cylinder, 16-valves 264hp engine designed by Opel.

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. 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. On the other hand, taking kerb weight as an important factor into account, Opel GT offers a marginal difference of 2% more metal.

Manufacturers have been building their reliability reputation for decades now and, generally speaking, it appears that Opel does have a slight advantage, all the models observed together. That's the official data, while our visitors describe reliability of BMW, as well as Opel, with the same average rating of 4.2 out of 5. Unfortunatelly, I don't have enough insight that would allow me to comment in more details on the specific models level. That apart, owners of different cars powered by the same engine as BMW Z4 rank it on average as 4.8, while the one under the competitor's bonnet gets 3.0 out of 5.

Both of the cars accelerate exactly the same, so we couldn't put one above the other. Car No. 1 reaches top speed of 229 kilometers per hour, 21km/h more than the other car. When it comes to fuel economy things look pretty much the same for both cars, averaging around 8.9 liters of fuel per 100 kilometers (32 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, BMW Z4 offers much better overall protection, which launches it ahead of the other contender. When it comes to performance, both vehicles provide similar experience, so I wouldn't point any of them out. BMW Z4 still consumps less fuel, which needs to be taken into consideration. All together, there's not much more to say, in this case I wouldn't even consider anything but 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™, out of 12.000+ vehicles we currently have in our database.