pg_advisory_lock(bigint) vs. LOCK TABLE

Hi,

What's the difference between below two queue implementations?
 -- -- With advisory locks. -- BEGIN; SELECT pg_advisory_lock((SELECT oid                            FROM pg_class
                    WHERE relname = 'queue')); DELETE FROM queue       WHERE id = (SELECT MIN(id) FROM queue)
RETURNINGid, val; SELECT pg_advisory_unlock((SELECT oid                              FROM pg_class
      WHERE relname = 'queue')); COMMIT;  -- -- With LOCK table command. -- BEGIN; LOCK TABLE queue; DELETE FROM queue
    WHERE id = (SELECT MIN(id) FROM queue)   RETURNING id, val; COMMIT;
 

Any helps will be appreciated. (BTW, yep, I'm aware of PGQ module of
skyytools[1].)


Regards.

[1] http://skytools.projects.postgresql.org/