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)
RETURNING id, 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/