My position is why either/or?
Use Cases, in all their variety, tend to be larger descriptions of
existing or desired features. Within this larger context, the team
(developers, users, etc.) should try to break down features in many,
smaller units of work. This is usually what's meant by User Stories.
So, yeah, you need a larger context in which to understand desires, in
which to determine what the next best small units of work to focus on.