Check it out here:
http://www.amsoftwaredesign.com/pg_vs_fb
When comparing in the grid the only major advantage FB has is probably
BLOB support.
PG only suppports 1 gb while FB supports 32gb. Bytea is pretty slow as
well when compared to the FB BLOB support.
The other area is Character sets and collation. They support it at a
field level as well as the database.
Other than that I would say PG kicks butt.
If there is any interest I could also add MySQL 5.0 to the mix as the
third column.
Later,
Tony