The G5 is the better cpu, but it depends on what you will be using the machine for. If you need to do alot of video rendering, video encoding and photoshop, a dual machine always helps, besides that, there is not much reason to get a dually.
I have the 1.8 G5 with the faster fsb, before they started making the slower ones with smaller HDs, and i have been happy for 2 years now.
You should also factor other things, like what each machine comes with, like, if the g5 comes with a combo drive and the g4 with a superdrive, hands down i would buy the g4 if it was the same or cheaper price (or more if not to much).
also, if you buy the g4 from apple you will most likely get the latest os, otherwise, any other online seller wont include tiger, but buying the g5, you are almost guaranteed tiger, unless it is refurbed from somone other than apple.
later
