On paper its the Prescott - it has a longer pipeline, its on a 90nm process, meaninig it can reacher higher clock speeds.
In reality its very close. Northwood has Hyperthreading, Prescott doesnt. Prescott (C0) runs very hot (although the D0 stepping has improved on this). Northwood is faster than the Prescott at the same clock speed (but only slighty). Prescott should be able to reach much higher clock speeds than the Northwood (130nm)
I think Intel needs a little more time just to tweak the 90nm process.
Does that mean the p4 now does even LESS work per mhz
Yes and no, Prescott should ramp to 4GHz and more on air and at this speed it might look better. Prescott was designed with HIGH speed in mind. It has a longer pipeline, etc...
But, in some calculations/applications the Prescott is faster than northwood at equal speed.
Now that Intel dropped the Netburst technology, we should watch carefully Dothan performance (Centrino), these processors sems to perform like AMD processor at equal speed, maybe it's even better. We must wait and see if Desktop Dothan will crush more per clock than AMD and it might be possible.
Lookin' to fill that <font color=blue>GOD</font color=blue> shape hole!