Case Logic Versus COALESCE Expression

PROC SQL;
      SELECT CUSTNAME,
        CASE
          WHEN CUSTCITY IS NOT NULL THEN CUSTCITY
          ELSE 'Unknown'
        END AS Customer_City
      FROM CUSTOMERS;
QUIT;

PROC SQL;
      SELECT CUSTNAME,
        COALESCE(CUSTCITY, 'Unknown')
        AS Customer_City
      FROM CUSTOMERS;
QUIT;