Phoronix published a review on the Windows 8.1 vs. Ubuntu 14.10 With Intel HD Graphics
A quote from the article:
For those curious how the latest open-source Intel Linux graphics driver is performing against Intel's newest closed-source Windows OpenGL driver, we've put Ubuntu 14.10 (including a second run with the latest Linux kernel / Mesa) against Microsoft Windows 8.1 with the newest Intel GPU driver released earlier this month.Windows 8.1 vs. Ubuntu 14.10 With Intel HD Graphics @ Phoronix