For the most part, video cameras are a very good tool to use to document a crime scene. The only real cons come if officers try to use them for too many things. If their limitations are acknowledged, they are something that is definitely good for use at crime scenes.
The main value of video is that it can allow people to actually see the crime scene in a way that is quite natural. Sketches of a scene do not tend to have the same immediacy as video and may not be as easily understood by human brains. Photographs can generally only show a small bit of the scene at once. Video cameras, by contrast, can show the scene as it would look if a person were standing at the scene and looking carefully around. This allows investigators who were not at the scene to better understand the scene and it allows juries to have a better feel for the crime scene as well.
The only real con about video cameras only arises if they are not used properly. For example, they do not typically have the picture quality that still cameras do. This means they cannot take pictures of fine details. They also do not tend to have as much zoom capability as still cameras. Therefore, they must be used to give an overall view of the crime scene, not as a substitute for still cameras.