David Welton <davidnwelton(at)gmail(dot)com> writes:
> I'm curious as to what the general opinion is on these different
> queries and their relative merits, especially in terms of speed:
You really should do EXPLAIN ANALYZE rather than assuming that the
planner's estimates are reliable.
The NOT IN case, at least, could be improved by increasing work_mem
to the point where the subquery fits into an in-memory hash table.
Larger work_mem would probably help the sorts used in the other
plans too.
regards, tom lane