Faster at what?
If you are going to do video editing as you are saying, there is no doupt that the G5 will smoke the others. The reason is simple: Dual processor and FCE/FCP. These software are light years ahead of the competition and you will save not hours but days when working with them instead of crap from the pc world.
That being said, the G5 is about at par with other top of the line intel box. Top of the line here means a computer that cost as much or more. Its totaly false to say that a G5 cost more than a PC, its same price or less (dont buy apple ram) and even better if you are a legit software user and pay licences for all your softwares.
The only place where the PC can be notably faster (10%+) is with games. Why? Games dont use dual proc and are never optimized for mac. Still the G5 will handle all games very well.
If you want a G5, here is a performance advice: get a RAID of Raptor drives. the investment is small and will increase your performence drasticaly.
I would like to conclude by saying that contrary with what computer makers make you believe, speed is the least important factor in productivity with a computer. Good software is the first thing, then its stability and finaly its speed. More than 90% of the time you are working, the computer CPU is idle, so even is a computer is 50% faster than another, you wil only save (at max) 5% of your time. On the other hand, a good software can cut your working time by half and that means gains in productivity up to 45%.
Get the best tool for the job, not what the manufacturer make you beleive you need. Go in a Mac Store and give a shot at FCP and you will see who awesome it is...
If you have more questions or need more info just ask, but first say what you will use the computer for...
