Speed is good.
If you're looking for compute power, you should focus on processor clock rate. However, video speed is determined by transfer rate over whatever bus the video is on. The memory bus speed is nonmonotonically related to processor speed. The new G3 PowerMacs have a 66 MHz memory bus. All the CPUs run faster than that, so their clock rate is divided down, by a small integer, to produce a memory bus rate no higher than the maximum allowed, e.g. 50 MHz.