Why is PGSQL better than MySQL:

John,  when i first started developing in open source,
i did a lot of research on dbs.  mysql had a HUGE,
HUGE, HUGE advantage in documentation at the time -
and that was a big factor since i'd be starting from
scratch.

i chose postgrsql inspite of this.  native foreign key
constraints was a big reason.  i came to like
transactions and it is more sql compliant than mysql.
it is also less buggy.

the license is also much more application developer
friendly - and this is HUGE if you ever want to
develop a product and market it.

having said that, mysql is an INCREDIBLY popular
database.  those people that know it inside and out
will not be inclined to change easily - the devil you
know is better than the devil you don't know...