It's a little known fact, one which Intel carefully hides, but a Pentium M is actually a Pentium III!
The one and only advantage that the P4 has over other X86 cores is that it can run at higher clock speeds. Thus, as the P4 speeds approach 4 Ghz, the AMD chips have barely passed half that. As AMD points out repeatedly, this does not mean that the P4 is faster. On the contrary, the two perform about the same. If anything, AMD has a slight edge.
While high clock speeds are manageable in a desktop, they are a serious problem in portable systems. Higher speeds mean more heat and more power consumption, both of which are deadly for portable use.
Like the AMD core, clock for clock, the PIII is much faster than the P4. So when Intel decided to come out with a new line of processors for portables, they went back to the old reliable PIII, changed the name, upgraded to a 90 nm manufacturing process, added a few power-saving features... and voila! The worn out old model has magically been restored to the full glories of her youth.