The Compare Utility (Diff) - Deep Compare
On the Baseline dialog, a "Recursively Compare" checkbox is provided. If set this will select a "Deep Compare", if cleared it will select a "Shallow Compare".
A Deep Compare will recurse through all packages and all elements immediately and fully populate the result tree. This is the best way to immediately load and see all changes, but may be very slow on large package structures.
The Shallow Compare is used on large packages, and only loads and compares the high level items first. As you click on nodes and open them up, if the node contains child items, they will be then "compared on demand" and the result shown in the tree. This lets you handle very large packages in a timely fashion and focus on only selected aspects of the model branch.