Just in general, I noticed the performance doesn't scale well with OpenGL effects compared to Catalytst. Turning on bloom alone in the new version of openarena is enough to slaughter the framerate by 1/8th on r300g. I don't have the benchmarks with Catalyst and bloom, but I'm pretty sure it doesn't get slaughtered by 1/8th.
The less OpenGL effects you stack up, the closer the open source driver gets to Catalyst.
I noticed PTS likes to turn on every graphics option, including non-default graphics options. So pay attention to the graphics option as even a single option in there can sometimes absolutely slaughter the framerate of the open source driver compared to Catalyst.
It's not that the open source driver is a lot slower, rather it's just a tiny bit slower at some effect and then that effect is getting multiplied by 100x per second which adds up quickly. Turning off the graphics option and the framerate increases multiple fold. For some games, it's just a matter of finding which switch is killing your framerate with the open source driver, and it's almost always an optional graphics option.
My graphics settings are maxed out. Still, I can't reach the low framerate I get with PTS.