I am surprised by the difference (even if it's small) between fetch and fetchrow_arrayref (your BC and DBC), as DBI docs say:
$ary_ref = $sth->fetchrow_arrayref;
$ary_ref = $sth->fetch; # alias
Or is the essential difference something else?
(Also, it would be interesting to have the DBMS version-numbers on those pages; it does say 2006, that's a long time ago. I would say that (arguably, no doubt) PostgreSQL has advanced more than the others in performance in this particular period)