Mac CPUs (I think Motorola is responsible..not sure) are much better designed than Intel (in particular ) chips, though. Intel are prone to chucking in totally useless stuff to try and get a higher clockspeed, like making a 20 stage piepline that has no benefit other than to push the clock cycles (but not performance) up. Or hyperthreading, which requires specifically written application.
Not to mention the overhead of having to preserve the old opcodes for backwards compatibility - i.e. complex instructions designed into the chip when machine / assembly coding was de riguer. Or having to try and cram in 32 bits without losing 16-bit compatibility.
On the other hand, when Apple created their 32 bit chip, they just redesigned from scratch - more efficient that way. I'd imagine ditto for this one.
It's worth noting that M/G hertz ratings are completely and utterly meaningless measures nowadays.... especially on Intel chips.