Conclusion
First of all lets talk about prices. Let's consider that
the two R9 280X together cost 422 Euro. Compare that to the
541 Euro you'd have to pay for the cheapest reference NVIDIA GeForce GTX 780 TI we can
find. Therefore this one high-end card is is about 23 percent more expensive than the
two mid-range models.
To dive a bit deeper into the results, we start with performance differences in
3DMark graphics score where we see that the CrossFire of the two R9 280X is between 50 and 53 percent faster
than the NVIDIA GeForce GTX 780 Ti. In the next theoretical test we ran, Unigine Heaven,
we see that the two R9 280X's are on average 18 slower than the NVIDIA GTX 780 Ti.
In case of games it turns out that for example in Sleeping Dogs one the one NVIDIA card is about 18 percent quicker than the two cards in CrossFire. A
closer look at Call of Duty Black Ops 2 shows the other end of the scale, where
the two R9 280X's score 32 percent better than the single NVIDIA GeForce GTX 780 Ti. In this case we see a rather huge variance in the test results.
Overall the two R9 280X cards are performing really well and there is no doubt
the two of them are seriously quick, actually, on average they're 9.1 pecent quicker than one GTX 780 Ti. But the problem is that the average value is not even telling half the story. It turns out that in quite a few games, the two 280X cards together are slower than the one GTX 780 Ti, which make performance rather unpredictable. Other than that ther is power consumption. In idle the power consumption of our test system is twice as high with the two R9 280X then with one GTX 780 Ti and under load conditions the setup with AMD cards can almost be used as a heating system. Concluding it can be said, that under certain circumstances the two R9 280X cards are quicker than one GTX 780 Ti and they're also cheaper but if you want to invest your money in an as sustainable way as possible, then we'd recommend to buy a single card.