• Hypergraph – Presents a graphical view of the scene hierarchy or dependency graph, with boxes representing nodes and lines representing relationships.

• Outliner- Shows a hierarchical list of all objects in the scene in outline form.

The Hypergraph
The Hypergraph is one of two main scene management editors in Maya (the other is the Outliner). The Hypergraph shows a network of boxes representing nodes and lines connecting them representing relationships. You can use the Hypergraph to view and edit hierarchical relationships (the same information the Outliner shows) or dependency relationships (input and output connections between attributes).
In the Hypergraph you can both see the DAG and the DG ?
The Hypergraph is a window that shows how the nodes and their connections are organized in your scene. You view object hierarchies and dependencies in the Hypergraph.
The Outliner
You can use the Outliner to examine the structure and components of the scene hierarchy, display shape nodes, connections, and attributes, select and rename an object, and reorder nodes
The Outliner is one of two main scene management editors in Maya (the other is the Hypergraph). The Outliner shows the hierarchy of all objects in the scene in outline form: You can expand and collapse the display of branches in the hierarchy, and lower levels of the hierarchy are indented under higher levels.
I find that the outliner is a good tool to use when it comes to get an overview of your scene or rig. It presents the hierarchy of nodes in a clear way.