i'm not so sure
what are you using the computer for?
I have a 2006 PowerMac G5 Dual 2.0GHz.
This computer is still quite fast, especially when you put more ram into it.
I haven't checked the specs but I think it would beat most early iMacs.
I don't think it's worth much anymore, so I would suggest it as the better choice for the reason that it is easy to upgrade hard disk space, RAM etc.
Also, it is possible to give it quite a boost with a new graphics card.
However, all depends what you are using, if new versions of software matter to you, I would agree that an intel machine would be better but if you are happy with Leopard and current apps, then the G5 is probably the better choice.