g5 vs g4 dual
I would check out barefeats.com and see if they list any comparison.
newer software will probably make a single g5 closer to a dual g4 in performance. CS 2 of adobe is optimized for g5, for example.
The g4 uses ATA-IDE drives
the g5 uses S-ATA drives
the g4 uses Simm memory (133mhz IIRC)
the g5 uses DDR3200 memory and holds a lot more
the fsb of the g5 is either 900 or 600mhz
the fsb of the g4 is 167mhz? or close to that.
There are a lot of differences, some programs will be faster by a ways on the g5, or a little bit faster on the g4.
The only thing I am lacking by not having a dual... the ability to use Quicktimes new HD codec (g4 wont do it either I bet!). And of course, with one processor, you might have to wait till something important like dvd authoring is completed to start another data intensive process.
$