I saw go with the Intel Mac. As mentioned by others, the G5 Macs do have reliability problems. The iMac G5s were all affected by the capacitor plague, despite Apple's repair extension program claiming that it's only the 1st-gen and some 2nd-gen models. Mine was actually not in the list of serial numbers (Rev B model with the ambient light sensor) but it was still affected by the same exact issue. Thankfully, Apple did change it when the repair extension program was still in effect. As a matter of fact, it happened to me twice in the same year, with only a 4-month duration between the first and second failure. If it were to happen again (God willing it doesn't), I would be on my own right now since the repair program expired in December of last year.

There are also issues with the Power Mac G5s from water-cooling defects to a few other issues on the older Power Mac G5 models.

The only reason to really stick with a G5 Mac is to run apps that require the Classic environment. This is moot in Leopard. Taking that into consideration, you're much better off today going for an Intel-based Mac, even if it's only a Core 1 model.