The sub-system can control the resolution , the number of colours displayed, the frequency at which the screen will be refreshed. It is often better to accept a smaller improvement by ensuring you get the maximum from your present card. Video drivers play a huge role in determining how well a video card will perform. The onboard video chipset is the single most important ingredient in video performance. You should know which type you have to facilitate locating and downloading new drivers.
Video memory affect how many colors it can show at higher resolutions.
The higher the resolution and color depth, then the more memory you need, because each and every pixel on your screen must have a space in video memory for its data. However increasing from 1MB to 2MB on a 64-bit video card will help performance. Video memory quality is of much greater importance to video speed. This specifies the amount of acceleration you want for your graphics hardware. Full acceleration is the fastest and is recommended for most computers.