AMD vs NVIDIA proprietary drivers performance?

[Zead]

That's the only article I have found, but that's enough I guess, thanks anyway.

Hopefully the AMD drivers will get better soon with the Valve pushing "Linux Gaming" forwards. Steam Machines ship with AMD cards too, pretty bad choice considering the poor performance on GNU/Linux.

My friend is buying a new GNU/Linux PC for gaming (since Windows 10 is a catastrophe), so I've told him to get NVIDIA, because of the AMD performance...

[rokytnji]

Phonorix usually keeps track of that

http://www.phoronix.com/scan.php?page=article&item=dirt-showdown-linux&num=1

[Zead]

So what's the situation on the performance between AMD and NVIDIA with proprietary drivers?

I've heard that NVIDIA drivers are better on GNU/Linux than AMD drivers. (In performance etc...) But these were years old articles. So what's the situation in 2015? Are the AMD drivers on par with NVIDIA drivers now? Or are AMD drivers getting better atleast?

Thanks.