This seems so easy and so trivial.  Just subtract Col A from Col B if
the answer is zero print column A (or B).  Here Cell C1 should be;
=IF(A1-B1=0, A1," ").  Next just drag (copy) the formula down the C
column.  Walla!  (and don't correct my bad french.  It is bad on
purpose)

Similarly as a check on my Gasoline credit card bill, I record the
Gasoline company and the dollar amount.  Example:
Column A   Column B
Shell            $30.00
ExxonMobil  $32.00
BP               $26.47
ExxonMobil   $50.00 (filled up the pickup)

Then I use SUMIF to sum and pick out the Dollars that go to each Oil
Col Credit card.
=SUMIF(A1:A10,"ExxonMobil",B1:B10).  Usually I get $82.00 as an answer.

Assuming your data does not allow you to do a line by line comparison, such
as =A2=B2 - copied down, you could set up two new columns and use
=ISNUMBER(MATCH(A2,$C$2:$C$6,0))
and
=ISNUMBER(MATCH(B2,$A$2:$A$6,0))
(change ranges as needed) which will return TRUE if the number exists in the
other column, FALSE if it does not.

Then use the autofilter on these new columns to get what you need (filter
one column or the either for TRUE to get numbers that exist in both columns,
filter the columns (one at a time) to get numbers that only appear only in
one, but not the other.  You could copy the results to a new location, if
needed.

ASAP Utilities, which is a free add-in easily found by Googling "ASAP
Utilities," makes this an easy job.

After installing the add-in, highlight the range that includes your lists,
and go to "ASAP Utilities/Information/Count Duplicates in Selection." This
will color the cells that contain duplicate data (regardless of order) and
give you a count of duplicates. Easy as pie.

Incidently, this is exactly the answer I gave to a posting just a few days
ago. You can often find answers to your questions by searching in the forum
-- also easy as pie: Just type a key word like "duplicates" in the search box
above.

Check out this web site of Chip Pearson.

Scroll down to the D's, and see all the articles on dealing with duplicates.

http://www.cpearson.com/excel/topic.htm