S-Video (Separated-Video) is better than a composite (RCA) video connection.
The bandwidth of S-video is the same as that of composite video. The real benefit of an S-video connection is that it can reduce dot crawl, hanging dots, and crawling edges that appear on the vertical and horizontal edges of some colored objects in the picture.
S VIDEO, originally known as "Y/C Separated video", is one of the higher quality ways to transmit the television signal from a peripheral device (DVD player, PlayStation 2, whatever) to a television. The way S-Video works is that it basically separates the color information (Chrominance) from the brightness (Luminance). By doing this, it reduces things like color bleeding and dot crawl and greatly increases the general clarity and sharpness of the picture. The reason that this is so is that televisions are designed to display separate Luminance (Y) and Chrominance (C) signals.