Both the Vibrance and Saturation sliders can be used to boost the saturation in an image. The difference between the two is that whereas the Saturation slider applies a linear adjustment to the color saturation, a Vibrance adjustment uses a non-linear approach. In plain English, this means that when you apply a Vibrance adjustment, the less saturated colors will get more of a saturation boost than those colors that are already saturated. This can be of real practical benefit when applying a saturation adjustment to a picture where you want to make the softer colors look brighter, but don’t want to brighten them at the expense of losing important detail in the already bright colors. In the Figure 1 example, I have demonstrated how a Saturation boost can easily damage the color information in an image. The other benefit of working with Vibrance is that it has a built-in skin color protector that should filter out colors that fall within the skin color range. This can be useful if you are editing a portrait and you want to boost the color of someone’s clothing, but at the same time, you don’t want to over-saturate their skin tones.
On the whole, I would suggest that Vibrance is the only saturation control you ever really need. However, the Saturation control remains useful still. As you can see in Figure 2, a Saturation adjustment is useful for making big shifts to the saturation, such as when you want to dramatically subdue the colors in a photograph.
this means that for desat effect, naturally saturation will be more useful than vibrance.
from my experience, vibrance does saturation in a more "natural" way than saturation.
i am not sure if you understood what they meant, but the gist i get is that saturation increases everything by the same amount. vibrance saturates the photograph, but does so nonlinearly, specifically.... at higher levels of saturation present, it will not saturate as much as it would at lower levels of saturation.
but there are always examples where strong saturation works, right? i'm sure you have seen it before. it depends on your preferences and what you want out of your photograph.