Overall, these results aren't too surprising (aside from the GTX 680 Xonotic performance oddity) given NVIDIA's proprietary driver is generally running at comparable speeds across all supported platforms -- even between Windows 8 and Linux -- and that SteamOS hasn't deviated too much away from upstream Debian at this time to warrant any real performance changes compared to Debian/Ubuntu.

Overall, the SteamOS vs. Windows 8.1 results aren't too far removed from other Linux vs. Windows NVIDIA GeForce graphics card benchmarking results delivered in the past on Phoronix. Generally the NVIDIA Linux graphics driver can deliver comparable performance to that of the Windows GeForce driver due to the largely shared code-base between platforms, which again is the case here with SteamOS just being a derivative of Debian Linux.