Since my last post, I have changed by opinion a bit. I spent more time playing around with World Book On-line for Kids & World Book Students. While there is a lot of overlap and repeated information, they also continue to build upon each other. For instance, World Book for Kids and World Book On-line for Kids are very similar, but one builds on the other. World Book Student continues to build with more information. You can see on article contents listed on the left, that the number of articles are more. When you click on a photo, you are offered more articles, pictures, and research guides. It also links you to more related websites. Of course, with my topic being camels, the research guide didn't really apply to my topic. I also like the quiz that was offered, since it gives students on opportunity to check what they learned and comprehended.
It really is true that the more time you spend at it, the more information you will find. Keep hunting.