GPU performance tests are nothing new, but the impact Windows 10 is having on render times is.
In a recent in a Blender performance test the folks at Lion Render (http://lionrender.com/2016/06/16/top-gpu-cards-performance-comparison-in-blender-gtx1080-titan-x-and-gtx980ti/)tested the EVGA GTX1080 (Founders Edition), EVGTA GTX980Ti, AMR R9 Fury, and TITAN X. Testing the cards across Windows 10, Windows 7 and Linux (Ubuntu 16.04) they found the operating system often mattered more than the card used.
They found performance gains up to 300% using Linux or Windows 7 over Windows 10. Some of this appears to be driver issues.