I like Macs, and have used some throughout the years. But for a reasonably priced machine, I don't think a Mac has EVER been as fast as a PC in real life use.
And the first Mac I tried was the very first monochrome one. The benefits of the earlier Macs was ease of use, but they were A LOT slower than DOS machines (obviously). When GUIs came around for Microsoft in a big way, the Mac GUI was better, but not really faster. And for the past several years, if you're talking games, a fast PC completely blows away any OS 9 based machine (not to mention that OS 9 is unstable). The PowerPC chips seem extremely fast, but the machine as a whole has never been stellar for speed, except for rare programs optimized for them. In fact, if you took a P4 1.4 and ran it against the fastest G4 using ALL of the Photoshop filters, I betcha the P4 would win on average. However, for some the P4 would suck @ss compared to the G4.
If someone is buying a G4 for speed, then s/he is fooling him/herself, unless the pocketbook is very deep. One buys a Mac for the GUI and the available software, features, and for personal preference.