AMD has been well behind NVIDIA in the last couple of years, but that might be about to change if these DirectX 12 benchmarks hold up.
It's an early set of benchmarks from Ars Technica UK, which has done a deep dive on the Ashes of the Singularity benchmark. It's the only publicly available game that has a DX11 and DX12 benchmark, allowing for a window into the kind of performance gains we can expect in a Windows 10 world.
What's interesting is the jump AMD cards have experienced. Ars was only able to benchmark a R9 290X against a NVIDIA 980 Ti, which under most circumstances wouldn't be a fair or a just comparison. Typically you'd want to pit AMD's Fury X against the 980 Ti or the TITAN X, but it was the highest end AMD unit they had available.
Nevertheless, the results were staggering and you should at least give them a once-over if you care at all about PC gaming. There's a huge explanation on the added features that DX12 brings to the table which explains some of why the results happened, but the sheer fact that an R9 290X managed to beat a GTX 980 Ti while running in 4K — even if it was only by one frame — is simply remarkable.
You can read the breakdown of the results, as well as comparisons at 1080p and 1440p across a range of CPUs, here. More competition always results in a better deal for gamers at the end of the day, and it'll be fascinating to see how this holds up once more DX12-enabled benchmarks and games become available.