diference in 12" powerbook graphic card vs upgraded 17"

I am just about to buy a 12" powerbook which would work perfectly for travel photography; but the apple store guy mentioned that the 17" powerbook has an upgraded video or graphics card or something and that card will not go with the 12".
Does anyone know about the advantages of this card?
I'm really not into gaming at all...just mainly concerned with the color, shaprness, contrast and overall accuracy of its ability to display my photographs.
Or maybe it makes the computer faster when doing batch processing in photoshop?
Any thoughts?
thanks,
M

It is also an option in the 15 inch, i have it, it is 128 vram instead of 64 vram, you probably will not notice a differnce, but if you want to go for the 15 inch go for it, or go all out and get the 17!