Difference between Content: Updated date and Content revision: Updated date in Views
I can see that the descriptions provided for both these filters can make things a little confusing. The below description and the image should help you out.

Content: Updated Date maps to node.changed and tells you the latest time when the node was changed.
Content revision: Updated data maps to node_revision.timestamp when a particular revision of the node (not necessarily the latest revision) was created.

You can check this in the query put together by Views, as shown in the image below. Hope this helps.