The higher of either is better. Typically computers come set for a resolution of 640 pixels wide by 480 pixels high and the color depth set to 256 colors. This is simple standard VGA monitor settings. Pictures are grainy and mosaic looking. Information on web pages runs off the screen and I have to scroll side to side.
Items seem larger than life.
The amount of video memory on a particular video card, determines the ultimate highest color depth and resolution it can produce. And there is a tradeoff. At some point, trying to increase the number of colors, will reduce the highest resulution the card can produce. Or increasing the resolution too high will force the card to display a lower number of colors. Those limits are what the amount of memory on the card, determines.