It's my understanding that the MacBook Pro runs windows faster than it's PC competition. If this is the case you would have the best of both worlds, the ability to run Vegas Fast and they option to use FCP if you needed to.
I run AMD processors. They run faster than anything.
The video card doesn't matter. If you're planning to do all of those things, though, I'd get a big screen with the highest resolution you can get. It'll make a bulky laptop, but the screen space is extremely valuable.
I use an GateWay MP8708. It has an intel core 2 duo processor T7200 that runs at 2.00 GHz with a couple of gigs of ram. The screen is BIG at 17 inches. I use it for Vegas 6.0 all the time.