Arshad said:
1) This new CPU is dual core in addition to other microarchitectural enhancements which make it more than 2x the theoretical performance of the older Intel CPU's that Mac's were being compared against. So it's no longer the same comparison -- the older Intel CPU's had less than half the computational power.
2) The G4 has always done poorly at the Spec benchmark for a number of reasons (a lot of which comes down to the compiler actually, and not the HW). Now Apple is using Spec as a benchmark to compare the two platforms and naturally this makes the delta seem even larger over the older machines.
3) In a lot of ways the PowerPC architecture is still technically superior, but that's a moot point now (with Apple anyways)
I've been working with Macs and PCs on a side by side basis professionally for 7 years, in the most demanding field for computers - digital video editing and compositing, and 3d modeling\rendering. Whether or not it's the hardware or the compiler, the simple fact is that Macs have always been slower than PCs for my work. Equivalent renders in AfterEffects take longer, rendering juicedrops in the Juicer takes longer, and 3d renders are just about interminable on Macs. It really doesn't matter to me if it's the hardware or the compiler - they're still slow.
As to the PowerPC architecture being superior - I just plain don't see it. I'm only speaking from my experience, but I run into just as many bugs and crashes on my dual 2.7 G5 at work as I do on my 3.2ghz P4 at home - usually more. Final Cut Pro, Apple's beloved DV editing child, simply crashes to the desktop probably 3 or 4 times a day - on BOTH of my edit suites. I'm running at least 4gb of RAM on each, Firewire800 RAID arrays by DVProject, and each machine is used exlusively for digital content creation - no extras installed, no games, nothing cluttering up the system.
However you want to slice it, they're just plain slower, whether you chalk it up to the software, or the hardware. Now, granted, I've yet to work on the Intel based systems, but if I have my way, our next HD systems will be PCs anyway.