BTW, since we're talking about burning a Leopard disk, it's worth mentioning that you need a drive capable of burning dual layer disks. I think all G5s came with a drive capable of this, but I don't know about even late G4s.
Only the last model PowerBooks came with a dual layer drive. In fact, in collector short-hand we often call these "DLSD" Powerbooks(dual layer super drive) although probably the most significant improvement for the end user is the higher resolution screen.
That's also not counting the cost of DL disks. You won't find a cake platter of them for $10-20 like you can with a DVD-R(BTW, for max compatibility with PPC Macs, err on the side of DVD-R rather than DVD+R).