OpenArena 0.8.5 is rather lax on modern hardware and does not even use GLSL shaders, but it has been one of the most common Linux games that has worked on the open-source Mesa driver stack the longest. When running OpenArena 0.8.5 on both Windows 7 and Ubuntu 12.04 with the latest Intel driver for the respective platforms, Windows 7 was 80% faster for the Sandy Bridge processor over the latest Linux development code and 50% faster with Ivy Bridge.
When running the new OpenArena release (v0.8.8) that actually uses GLSL, supports bloom and HDR and other new visual rendering features, the Linux driver is not as far behind. However, Ubuntu 12.04 with the Git Intel stack still loses out. The Core i5 2500K with its HD 3000 graphics were 37% faster with Windows 7 and the HD 4000 graphics on the Core i7 3770K were 14% faster.
Warsow is one of the more demanding modern open-source games and is powered by the Qfusion game engine. The i5-2500K was 68% faster under Windows and for the i7-3770K was 50% faster under Windows.