Right now? Probably not much, other than that it can be linked to a user account.
However, in the future, with multiple user accounts with individual permission levels and device trackers tied to them, the new area’s component with the ability to have a “person” in an “area”, etc, there will likely be many differences.
With the initial introduction of this component there is not much difference, but it might make sense to migrate to it where possible so when more advanced features are added the transition is smoother.