Assassin's Creed 4 Black Flag
Uh oh. Click through the plots above, and you'll see occasional frame time spikes from AMD's multi-GPU solutions, both the HD 7990 and the R9 295 X2. Those same spikes are absent from the plots of the R9 290X and the two GeForce configs. The spikes have a fairly modest impact on the 295 X2's FPS average, which is still much higher than a single 290X card's, but they're reflected more clearly in the latency-sensitive 99th percentile metric.
The 295 X2 is still faster than a single R9 290X overall in Black Flag, but its multi-GPU scaling is marred by those intermittent slowdowns. Meanwhile, the GTX 780 Ti SLI setup never breaches the 33-ms barrier, not even once.