Benchmarks: 1080p & 1440p
Testing at 1080p using the highest quality in-game settings along with 4xMSAA, the GTX 980 Ti is still able to just edge out the Fury X in both the DX11 and DX12 modes. The Fury X was just a single frame slower when using DX12 while it was 7fps slower in the DX11 test. The larger margin under DX11 is believed to be down to the fact that Nvidia has optimized its driver for DX11 performance in Ashes of the Singularity whereas AMD hasn't. It's interesting to note that the Fury X is still only 6% faster using DX12 when compared to DX11, though we are testing with a Core i7-6700K here.
Similar margins were seen between the R9 390X and GTX 980 as well as the R9 390 and GTX 970. Finally, the R9 380 and GTX 960 delivered similar DX11 performance while the 380 was considerably faster when testing with DX12. It is also interesting to note that here the 380 was slower when using DX12.
Bumping the resolution up to 1440p only has a minor impact on performance, the trends all remain much the same and on average just a reduction of 5fps is seen across the board.