...I think he wants to know about a MB - not a MBP.
I think there are a few folks here running FCS2 on a MB but can't swear it. I don't know how much grafix they do either. I would go with a MBP just for the sheer ballz of it. My 17" MBP 2.6 Core 2 Duo / 4 Gigs of RAM / Hi Rez Widescreen handles all my editing (FCS2), grafix (AE / PS / ILL CS3), 3D apps (Cinema 4D 10.5) & finishing like butter. It also runs a second 30" monitor from the DVI port. With the right peripherals it will probably make my coffee & fix my Jeep as well. Best machine I ever owned. Wanna buy a Quad Core PPC?
When life gives you dilemmas...make dilemmanade.