Phoronix compared the performance of Ubuntu 12.04 vs. Windows 7

Here's a comparison of the Ubuntu 12.04 LTS versus Microsoft Windows 7 performance when it comes to using Intel Sandy Bridge and Ivy Bridge processors with integrated graphics. While the Sandy Bridge graphics performance was once faster when it came to OpenGL with the open-source Linux driver, that's no longer the case. The Linux OpenGL performance for both Sandy Bridge and Ivy Bridge hardware is now slower in most GL workloads than Intel's Windows 7 x64 driver.

  Ubuntu 12.04 vs. Windows 7: Intel Sandy/Ivy Bridge Loses On Linux