I like the potential to use all three of the Britannica levels in order to provide information at various reading levels. It could be helpful for teachers to see this so that they can provide reading on a topic for a variety of students in the same class. Yes the amount of information varies, but at least the students who are struggling readers are also able to be reading about the same topic.
I also like the "workspace" feature so that students can quickly save information and be able to access it at a later time. I often find that they run out of time to be able to read, process and take notes on information, so this will make it easier for them to get back to it at another time.
The country information in the High School edition is great for the basic facts as well as the link to the other websites which give more detailed information.  I also really like the ability to share the workspace with others. If a teacher creates an assignment and then wants students to have some specific reading material to go with it they can share this, rather than print it to give to the students. The students can always get to the information, rather than complaining that they've lost it or can't find it.