Nouveau vs. Radeon vs. Intel Tests On Linux 3.16, Mesa 10.3-devel
Unvanquished on Nouveau with the Kepler GPUs does better than the AMD GPUs using the RadeonSI Gallium3D driver except for the oddly fast performance out of the R7 260X.
The open-source AMD stack does better than Nouveau for Warsow before becoming CPU limited.