If you would like to make an exact copy of one of your contact accounts, a clean sync is appropriate. A clean sync involves completely deleting one of your accounts, and then syncing your contacts so that they match.
- From the Contacts Menu, select "Delete All Contacts & Groups" and delete the desired account.
- From the Sync/Move Menu, select "Sync Contacts" and "Standard," and perform a "2-way sync."
Now your two accounts should exactly match.