Quake 3: Arena
Sound on or off, the Radeon 9800 Pro is limited by the dual 1.25 GHz G4s. Nonetheless, it is able to turn out impressive timedemo scores in excess of 150 FPS at 1600x1200 — unprecedented on the Mac — while the performance of the other two ATI cards are quickly bound by their fill rate. And if the numbers on Apple's Power Mac G5 graphics subpage are accurate, then it should be capable of over 300 FPS at low resolution. Although this isn't necessarily indicative of performance in other games, it's nice to know that you can play at a high resolution without a sizeable decrease in framerate.
Unreal Tournament 2003
UT2003 doesn't utilize dual processors as well as Quake 3 does, but the benchmarks tell a similar story. There is a slight aberration at low resolution, though, where the Radeon 8500 and 9000 Pro's minimum framerate is about 20% higher than the 9800 Pro. This may be attributed to the "wrapper" design of the drivers and the overhead from the card's features. The minimum framerate is a more revealing statistic than either the average or maximum framerate. It determines how "smooth" gameplay is and the higher it is, the less you'll experience jerkiness. Of course, at high resolution, the Radeon 9800 Pro completely out-muscles the other two cards.
As an aside, notice that the Radeon 9000 Pro has an advantage over the Radeon 8500 in Quake 3, but the tables are turned in UT2003, where the second texture pipe of the 8500 is fully utilized.