@mindbend and everyone else trying to keep this thread constructive:
Because there haven't been any major updates to Maya since the G5 was released, I would assume that there are no G5 optimizations in Maya at all, and that could be the source of many performance discrepancies. There is a lot of G4-related code in Maya right now, but those performance tweaks don't necessarily carry over to the G5. I'm not privvy to any insider information, but my guess is that the next major version of Maya (5.5 or 6 or whatever they hell they decide to call it) will hopefully have at least some G5 optimizations.

Also, I wouldn't do any performance testing with Maya PLE, mostly because it doesn't support dual processors. Create the same complex scene in Maya Complete, and you're probably going to see some performance increases, especially on a dual-proc system.

@vladimirjp:
If you're "OS war'ed out" as you say, then why did you even bother posting? Your comments are highly opinioned and not even remotely constructive. Mindbend posted an honest question looking for information. Your blanket statements on how Macs are "fancy and flashy useless machines" and how Macs are "for the not so computer savvy" don't help answer the questions and actually end up creating a flamewar. If you can't say anything useful, then don't post.