Aperture works ok on my MB 1.83 CD w/ 2 GB RAM, it'll work well on a MB 2.0 C2D. You will see a noticable benefit from the MBP due to it's better GPU, but the C2D in the MB is so fast that it compensates a lot of the lacking GPU power.
I'd rather get a MB instead of a MBP and invest in good equipment like a graphics tablet, 2nd screen etc.