PostgreSQL DBMS Notes CompareData
PostgreSQL ANSI Fair

Driver does not convert wide char source data to narrow char on synchronizing data. For example inserting SQL Server nchar data 'abcdefg' results in only 'a' being inserted.

If the schema of a DBMS comparison side (SQL Server or Oracle, for example) has wide char columns (SQL_WCHAR, SQL_WVARCHAR, SQL_WLONGVARCHAR) then use the Unicode version of the PostgreSQL ODBC driver until this issue is resolved.