What's the Difference Between a 128mb nVidia Video Card and a 383mb?

I'm thinking of buying a new Media Notebook (to be specific, a Dell Inspiron 1520 and HP dv6500t) and want a nVidia Video Card. Yet, i'm a bit confused about one part. Both Computers can be installed with the NVIDIA GeForce 8400M GS. Yet, the HP has a 383mb version, while the Dell has a 128mb version. Is there a difference between the 2? And which is better to get?|||Assuming both cards have the same features, the card with the larger video memory will give you a faster game computer, especially with action games. I suspect the card with the larger memory will allow you to use additional features in the included software that will make the pictures sharper and video smoother.|||More memory is always better to get! If your playing a game and you run out of memory from textures or something you'll suffer big performance losses. More memory forever!!!