I'd explore Delete Identical (Data Management)Delete Identical (Data Management Toolbox), which removes all but one of the identical records found. As a ArcToolbox tool, you can use it in scripts, or directly from the GUI.
To list the duplicates without deleting them, the Find Identical tool is also available, using the "Output only duplicated records" parameter. However, this outputs a new table, rather than creating a selection in your original data.