What graphics/video card should I select

There are both ATI and NVidia graohics/video cards and I am trying to decide which to chose.  What is the best card to select?

ATI makes ATI Mobility Radeon HD 5850 graphics with 1GB of DDR5 VRAM and 1024 (MB) ATI Mobility Radeon HD5870 while NVIDIA has a  NVIDIA® GeForce GT 445M 3GB graphics and 1024 (MB) NVIDIA GTX285M GeForce

How can I decide what the best card is when getting a new laptop from Dell.  Just from the description it sounds like the 1 GB ATI card is lacking since it is only 1 GB compared to the other cards.