I see. So the Object ID points to the template from which all other instances of that object or template are created. The Unique ID points to an instance of the template and is unique across all instances of any template. Instances of the same object will all have the same Object ID, but everything in the game has its own Unique ID.
Also, it seems that you can reliably "Create Object By Name" and pass an Object ID instead of an object's name. Passing a Unique ID to "Create Object By Name" will not always work.
I'm aware that OIDs and UIDs are only reliable at runtime and may not have the same values across different runs.