Smokin Guns, which is another ioquake3-based creation, is a game where the Gallium3D and classic Mesa drivers for R300 and R600 performed the same. On average across the different GPUs and drivers, the Catalyst 10.12 driver was 5.75x faster than the latest open-source Linux code.
Tremulous, the last ioquake3 game tested, shed some slightly different results. This time around at 1920 x 1080, the Tremulous game did slightly better with the classic Mesa driver than Catalyst. However, all of these graphics cards produced playable frame-rates at this HD resolution. The open-source drivers crept closer to the Catalyst performance, but still the binary blob was three times faster.