Power Consumption & Temperatures
Although the GTX 960 SLI cards were 20% slower than the R9 280Xs in Crossfire when testing Bioshock Infinite, Nvidia's setup also used 29% less power so it's slightly more efficient.
When testing Metro: Last Light, the GTX 960 SLI cards consumed 30% less power than the dual R9 280Xs. Note that when benchmaking frame rate performance we used Metro Redux.
When measuring system power consumption with Tomb Raider we find that the GTX 960 SLI configuration consumed 28% less power than the R9 280X Crossfire cards, which is all the more impressive considering the fact that the GTX 960s were 7% faster.