I think the 2:1 ratio is about right. The PowerPC is more efficient - it gets about as much work done in one clock cycle as a Pentium does in two cycles.
There are a couple of other factors to consider -
Modern Macs have Quartz Extreme, which greatly improves video performance. Windows won't have a similar hardware acceleration architecture until Longhorn is released, at the earliest.
Some Mac software uses the G4/G5 vector processing units which will easily outperform Pentium software running at much higher speeds.
Doesn't really matter what we think - what matters is what we can prove, and I think that claim will be tough to prove.
Yeah, but windows machines have Mach 5 radical edge with the quadrophonic Blaupunkt. It blows the Quartz Extreme away.