How much difference does the memory on video cards make?

so if you had to of the same but one was 256mb and the other was 512mb. would the 512mb have any big difference in gaming?|||Yes. And depending on the game. Some games will not install if you video card doesn't meet the requirements. You will get lag in your game if you try to play with a video card that is way less than the requirements.|||It makes huge differences in gaming.