AnandTech: Apple Makes the Switch: iMac G5 vs. iMac Core Duo
Really good performance comparison on AnandTech between the iMac G5 and the iMac Core Duo. I especially like when they disable one of the cores on the Intel chip and pit it against the G5. From my view, this says that the PPC architecture was good, it's too bad IBM didn't care or wasn't fast enough in competing with Intel and AMD on dual core and low power designs.
Anyway, technically it won't make a differnece how good the G5 is when you can run Windows and OS X on the same hardware.