A few days ago my benchmarking revealed Windows 8.1 is outperforming Ubuntu Linux with the latest Intel open-source graphics drivers on Haswell hardware. I have since conducted tests on the Celeron N2820 NUC, and sadly, the better OpenGL performance is found with Microsoft's operating system.
I recently decided to buy another Intel NUC DN2820FYKH after having great experiences with the first one and it's still running great with Fedora 20. This ~$140 NUC has an Intel Celeron N2820 "Bay Trail" SoC that's dual-core and running at 2.4GHz with a 7.5 Watt TDP and Intel HD Graphics that clock up to 756MHz. With this NUC build I installed a 1TB HGST SATA HDD and 4GB of DDR3L system memory.
I first benchmarked this N2820 NUC with Windows 8.1 after applying all system updates as of last week and using the latest Intel Windows 8.1 graphics driver for Bay Trail. On the same NUC I then installed Ubuntu 14.04 with all available updates and using the Oibaf PPA for obtaining Mesa 10.3-devel, since Mesa 10.1 as shipped by default in Ubuntu 14.04 is very slow for the Bay Trail graphics. After benchmarking Ubuntu 14.04 LTS with Mesa 10.3-devel and its default Linux 3.13 kernel, I then installed the Linux 3.15 development kernel and repeated these Intel OpenGL gaming benchmarks. No changes were made to the hardware during the testing process under Windows 8.1 and Ubuntu 14.04 Linux.
All benchmarks were conducted using the Phoronix Test Suite.