I have been working on the Cocoon nebula and have colour RGB data as well as Ha data. During the processing I was able to see the huge difference between the RGB and Ha in this instance. I decided to do a quick animation so that you could appreciate the massive difference yourself.
The first image is RGB data taken using a mono camera. This is the sort of Cocoon nebula image that we are used to seeing.
The second image shows what happens when the Ha data is added to the red channel - Here you can see the extra detail that is added into the image that you can't see at all in the RGB image.