Is there a meaningful benchmark?

Hi. I'm writing up a database comparison paper in my department at
work, with Postgres being a major candidate. I have been attempting to
research various issues and provide a meaningful comparison.

One issue I would like to give some kind of information on is
comparative performance. When I look for such things in Google or
Wikipedia or the pgsql email archives, it's hard to find anything
reasonably definitive. I've found isolated claims and anecdotes here
and there, and a fellow on the list here who attempted to do a
comparison between Postgres, MySQL, and Oracle but gave it up for now.

Some of the claims I've seen said that in some cases MySQL with MyISAM
ran 2x faster than Postgres, but that may have been for a special case
with only read access to the database; whereas another one claimed that
MySQL with InnoDB was slower than Postgres. Other people commented that
it depends on how you tune the databases.

Maybe there's nothing definitive out there. However I'd like to get a
ballpark idea of how some databases compare, using some kind of average
case schema and application, in terms of transactions per second, on a
common hardware platform. I would like to be able to point to a
reasonable reference, rather than engaging in handwaving myself.

Does anyone know where I could look?

-Will