Performance of PostgreSQL vs. Other DBs

Hi,

I am currently trying to sell the usefulness of PostgreSQL to my company (A consulting firm). I need a couple
convincingarguments. One thing that I was unable to find good comparisons of is performance of PostgreSQL vs. Others
(Oracle,SQL Server, Sybase). Does anyone have any benchmarks that I could use to demonstrate performance of PostgreSQL
againstthese other databases.  

By the way, even if PostgreSQL lags a little behind these numbers would still be helpful to me for 2 reasons:

1) A little lag would still show that it is almost equivalent with databases which cost significantly more.
2) Whether I should actually be pushing towards PostgreSQL if it is not performing well enough.

Thanks to anyone who can give me some information on this. Any info is greatly appreciated.

Mirko