Originally Posted by
DanK
The saturation adjustment increases saturation uniformly, while the vibrance adjustment is intended to increase the portions of the image that are relatively unsaturated. In general, my experience fits with this: saturation is a blunter tool and often leads to unnatural-looking images. For that reason, like Manfred, I rarely use the saturation adjustment. I save it for images that are flat across the board. In contrast, I use a modest vibrance adjustment in almost all images, because I find that helps the adobe standard rendering, at least with my cameras.