I would personally not get an iMac at all right now. But, if I had to choose purchasing between a G5 iMac and an Intel iMac, I'd choose the Intel system.
I've owned 2 of the last 3 revisions of the iMac G5, and I hardly got any use out of them because they were always being repaired at the shop.
The only parts I never had replaced were the CD-ROM drive, hard drive, and foot / stand.
I'm not kidding. Every single other part was replaced. This includes the case, keyboard, mouse, power supply, logic board, LCD screen, and more. Some of those items, including the LCD screen, were replaced more than once.
I have seen my iMac G5's die more than anyone could possibly imagine. They just kept dying.
So, I can't imagine buying another iMac until they move to an entirely new design (and I mean entirely new design - including the case and LCD screen).
But, if I were forced to choose between one and the other, I'd go with the Intel iMac as it is at least less problematic than the G5.