I have heard mixed reports about weather or not the MBP has a mobility card or not, and also if the iMac has a mobility card or not. I'm pretty sure that mobility or not, both machines have the same cards.
The two machines have the same clock speeds and RAM speeds, and can support the same amount of RAM.
The ONLY difference in the two machines I can see is the HDs, 5400 v 7200, though this can be sloved by ordering a 7200 in the MBP.