Increased performance from single statement, multiple row inserts?
There is a big difference. Insert as many rows as possible at once. Best in a single INSERT statement, but at least in a single transaction. Inserting individual rows takes much longer. Quoting the chapter Populating a Database:


  If you allow each insertion to be committed separately, PostgreSQL is
  doing a lot of work for each row that is added. An additional benefit
  of doing all insertions in one transaction is that if the insertion of
  one row were to fail then the insertion of all rows inserted up to
  that point would be rolled back, so you won't be stuck with partially
  loaded data.


If you insert a large number of rows, consider COPY, which is much faster, yet. And read that chapter in the manual. It has all you need.