Similar queries taking different times to complete
These 2 queries are not the same and don't return the same result . 
You end up with following filters:

1st Query:

 WHERE
 (
 a &gt;= To_Date('&amp;&amp;1','YYYYMMDD')
  AND a &lt; To_Date('&amp;&amp;1','YYYYMMDD')+1
 )
 AND 
(
    b LIKE ...
   AND e IS NULL
   AND adjust1&gt;0
   AND (b NOT IN ('...','...','...'))
   OR  (b = '... AND c &lt;&gt; NULL)
)


Second:

WHERE
  (
  a &gt;= To_Date('&amp;&amp;1','YYYYMMDD')
  AND a &lt; To_Date('&amp;&amp;1','YYYYMMDD')+1
  AND b LIKE '..'
  AND e IS NULL
  AND (b NOT IN ('..','..','..'))
  )
  OR  
 (b='..' AND c &lt;&gt; NULL)


You need to use parenthesis carefully while combining  AND and OR predicates in one condition.