It depends on the card... If its a low end card it won't be able to use the 2gb of ram no matter what the memory bit is - and it being a 128-bit means it is a low end card so the 2gb is totally pointless. That being said the only way the 1gb 256-bit card would have issues is if it was a high end card, but high end cards don't have 1gb anymore so i assume its a low-mid range so 1gb is plenty(any more ram would be pointless because the card would not be powerful enough to use it anyway). SO based off the little information you gave us I would assume the 1 gb 256-bit card is the better of the two.