How can I do a differential query (delta plus/minus) telling me what rows are in view A that are not in view B and vice versa?
You can use a FULL OUTER JOIN for this

WITH T1
     AS (SELECT trantype,
                product_code
         FROM   vwVIEW1
         WHERE  KEY = 'DEMO'),
     T2
     AS (SELECT trantype,
                product_code
         FROM   vwVIEW2
         WHERE  KEY = 'DEMO')
SELECT *
FROM   T1
       FULL OUTER JOIN T2
         ON T1.trantype = T2.trantype
            AND T1.product_code = T2.product_code
WHERE  T1.trantype IS NULL
        OR T2.trantype IS NULL