Kinda. Actually, the PowerPC 970 can run fully in either 32 or 64-bit mode, so that wasn't the issue. The G5s, and late-model G4s (AlBooks, iBook G4s, G4 towers w/FW800, eMacs w/USB 2.0), won't run OS 9 because nobody wrote drivers for the newer hardware, in addition to the fact that OS 9 wasn't recognized as a valid OS in firmware (for obvious reasons).
Anyway, according to Apple's own internal tests between the early Mac Pros and the last G5s, the G5 still outperformed the Intel chips at various tasks, such as certain PhotoShop filters and the like. This may be simply because certain apps weren't fully Intel-compatible, or it may be because the G5 was a fairly decent setup.
Google may still be able to turn up the comparisons, if you're inclined to look for them.