Keep in mind that whenever issuing an Administrative Template setting that is unmanaged, or when deploying a GP Preference, your settings could be overwritten by the user's own hands. Policies are traditionally set firmly into place so that the user cannot manipulate them, that is kind of the point of Group Policy. Preferences, on the other hand, are just that—configuring preferred settings to make a user's life easier or more efficient. Many things inside Windows Settings or the Control Panel are good examples. You may use preferences to manipulate all of your machines to behave one way when they are deployed, but perhaps your users want to tweak those settings to their own liking. Maybe items such as screen settings, mouse settings, or speaker settings—things of that nature. So Group Policy sets it to your administratively-defined default setting, and then allows the user to overtake that setting and change it according to their own preferences.