Thats to do with the memory bandwidth on the card, which will impact performance not image quality.
So as to whether the image will appear distorted, off colours and bad contrast settings. No the memory bandwidth does not affect these things. For that you want to be looking at the monitor and connection you are using.
If you are looking for high levels of graphical detail, basically higher settings in games and such, then the memory bus will become important with settings that rely on the VRAM performance (Anti-Aliasing and displaying to higher resolutions in particular).