Significant difference between contains and containstable?

Question

I have a full-text index created upon a column of type varchar(max) with filestream enabled. The filestream contains data such as JPG's, TIF's, PDF's, and XML's (although this is mostly irrelevant to the question, I believe).

I have two queries that I've created that allow me to search upon the index.

Full-text search #1--

select
      parentObj.ObjectID as 'GroupingID',
      parentObj.Name as 'Grouping',
      childObj.ObjectID as 'FileObjID', 
      childObj.Name as 'FileName',
      fs.FileStreamID
    from dbo.dat_FileStream fs
    inner join dbo.dat_Object childObj
        on fs.ObjectID = childObj.ObjectID
    inner join dbo.dat_Collection c
        on fs.ObjectID = c.ObjectID
    inner join dbo.dat_Object parentObj
        on c.ParentID = parentObj.ObjectID
    where contains(FileStreamData, @srchTerm)
        and parentObj.ObjectTypeID = 1
    ORDER BY 'Grouping'

Full-text search #2--

select
      KEY_TBL.RANK,
      parentObj.ObjectID as 'GroupingID',
      parentObj.Name as 'Grouping',
      childObj.ObjectID as 'FileObjID',
      childObj.Name as 'FileName',
      fs.FileStreamID
    from dbo.dat_FileStream fs
    inner join containstable(dbo.dat_FileStream, FileStreamData, @srchTerm, 1000) as KEY_TBL
        on fs.FileStreamID = KEY_TBL.[KEY]
    inner join dbo.dat_Object childObj
        on fs.ObjectID = childObj.ObjectID
    inner join dbo.dat_Collection c
        on fs.ObjectID = c.ObjectID
    inner join dbo.dat_Object parentObj
        on c.ParentID = parentObj.ObjectID
    where parentObj.ObjectTypeID = 1
    ORDER BY 'Grouping'

The only significant difference between the two full-text searches is query #1 uses contains and query #2 uses containstable.

My problem is that the two queries do not always yield the same results. For example, were I to search on the phrase "Independent contractors", query #1 would yield a result set of 10 different documents (PDF's and XML's), while query #2 would only yield a result set of 6. This seems to be the rule: query #1 always yields a few more than query #2, and query #2 always yields the exact same matches that query #1 does.

Query #1 - search on "Independent contractors" yields:

4262    AAA-00-12   4561    AAA-00-12.pdf   4235
4316    AAA-00-15   4753    AAA-00-15.pdf   4427
4316    AAA-00-15   4754    AAA-00-15.xml   4428
3873    AAA-00-19   4784    AAA-00-19.pdf   4458
3903    AAA-00-22   6795    AAA-00-22.pdf   6459
3953    AAA-00-24   6899    AAA-00-24.pdf   6563
3953    AAA-00-24   6900    AAA-00-24.xml   6564
4842    AAA-00-9    4905    AAA-00-9.pdf    4577
4842    AAA-00-9    4906    AAA-00-9.xml    4578
4057    AAA-0001    4260    AAA-0001.pdf    3936

Query #2 - search on "Independent contractors" yields:

19  4262    AAA-00-12   4561    AAA-00-12.pdf   4235
126 4316    AAA-00-15   4754    AAA-00-15.xml   4428
126 4316    AAA-00-15   4753    AAA-00-15.pdf   4427
116 3873    AAA-00-19   4784    AAA-00-19.pdf   4458
125 3903    AAA-00-22   6795    AAA-00-22.pdf   6459
57  3953    AAA-00-24   6900    AAA-00-24.xml   6564
57  3953    AAA-00-24   6899    AAA-00-24.pdf   6563

Answer 1

CONTAINSTABLE:

top_n_by_rank

Specifies that only the nhighest ranked matches, in descending order, are returned. Applies only when an integer value, n, is specified. If top_n_by_rank is combined with other parameters, the query could return fewer rows than the number of rows that actually match all the predicates.

Try running w/o a top and see if it matches CONTAINS.