Advantage: You can see where clouds are developing, long often long before showers and thunderstorms are visible on radar.
Since all clouds are visible, you can see different motions in the winds in the atmosphere.
Disadvantage: Obviously, only useful during daylight hours.
All clouds, whether low to the ground or high in the atmosphere appear the same so you cannot determine heights.
Also, in winter, it is often difficult to tell the difference between snow cover and clouds with the visible image.
This is a late afternoon visible image of the tops of strong thunderstorms over Arkansas January 21, 1999 and shows the level of detail available.
The strong updrafts are poking through the tops of the thunderstorms (overshooting tops) casting shadows to the to the northeast of each updraft.
This view is created as the strong updraft rises into the stratosphere. When it does the updraft collapses giving this bubbly appearance.
However, if the sun elevation was high overhead, the depth perception would have been lost which make it difficult to determine the cloud type and height.