The CPU and FSB are the same on both machines, so it's equal there. However the iMac has a discreet GPU, whereas the MB doesn't.
Both the iMac and MB use mobile CPUs, which are very similar - the iMac's CPU is an overlocked (FSB) old Santa Rosa CPU, whereas the MB has the new Montevina CPU.
Unless your editing programs (eg CS4) touches the GPU, the MB and iMac should be the same in terms of power - if there are any differences however, they will be very very minimal and un-noticeable.