In 4.2.e, the Move Dialog opens with the folder tree on the right expanded to show the location of the current file. This makes it much easier to move a document into a neighboring folder, as the user doesn't have to browse to find it.
In 5.1.c, the Move Dialog opens with the folder tree on the right only showing the top level of folders.
The dialogs otherwise look and behave identically.
The screenshot below shows this issue. In this case the node is 6 levels deep, but the picker only shows the first level in the site and the root node is selected.