You're not going to get anything (comparatively) decent in a notebook, therefore anything that's not shared is a bonus. Doesn't really matter what you get, due to other limiting factors of notebooks, the performance isn't going to be vastly different between a GeForce or Radeon.
You might also want to look into the GeforceFX Go 5600 (64MB) / 5650 (128MB) / 5700 (128MB). Ive seen reviews of laptops getting over 10,000 3dmark2001 marks with these cards. These will easily play any game you throw at it (ok, you might only get 300fps where on a 9800XT you would get 400fps )