A good example is how deep the transactional DDL features go--Oracle has started to catch up recently, but PostgreSQL still has a lead there. The ability extend the type system and indexes with your own custom items are also better in PostgreSQL than any other database. This is why the PostGIS add-on (built using the type extension facility) is busy displacing installations of the weaker Oracle Spatial at installations all over the world right now.

PostgreSQL
setup a database system
create my users
set my permissions
and create my schema.
know the basics of a relational database system:
* SQL,
* triggers,
* stored procedures,
* vistas

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The access to the database should go through an API that is designed and implemented separately from the database. Web services are the obvious example.
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http://stackoverflow.com/questions/5975907/postgresql-vs-oracle#_=_
Put yourself these questions:

1) Do I really need RDBM? Every insert/update/delete costs very much. When you define foreign keys and other constraints it costs lot more.

2) Who is going to support your website (and database)? Oracle is world famous for its configurability and great world wide support. You can get Oracle specialist in every country in the world. You can order consultancy and possibilities are pretty high. Its easier to get a support company (or a contract) for Oracle than PostgreSQL. But if you are going to support yourself (your company) then you could go for PostgreSQL.

3) Is there any feature that have only one database? You wont make use of advanced features of both database platforms most likely, but check what you need. If you need replication, backups and other things go and read documentation for both platforms. They both offer such a features, but its better to be prepared. Maybe you will need some feature that only Oracle has. It can happen.

Back to your question. Oracle usually wins for it's support and additional features. But to someone surprise many projects (companies, products) do not make use of the support or these features. If you check all the features you need PostgreSQL can do the work for you.

Big companies usually stick with one database platform. When they buy an Oracle license once (and employs db specialist), they buy next time. That's the rule. But you have free hands now. Draw on!

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My opinion is that PostgreSQL is very close to Oracle, especially with the upcoming 9.1 which offers an alternative to Oracle's DataGuard.
On the SQL Level there are really head-to-head, not much difference.

Things where Oracle offers still more features:
Materialized views (and all the related magic)
Flashback queries and flashback archives (they are really cool)
Index only scans (can be a major performance boost)
No transaction control in stored functions

As much as I like PostgreSQL one thing that can be really annoying is configuring (auto)vacuum to cope with high write traffic.

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Support
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As for support, there are half a dozen companies in the world you can buy PostgreSQL support from at a fraction of the rate Oracle charges for it. I routinely fix bugs in the database itself within hours of report for my customers, as part of a service contract, which is an option on top of the free community support. Because PostgreSQL is open-source, there are multiple vendors available who provide this service. With Oracle as a closed source product, there can only be one who is capable of offering this quality of support. And that single source vendor has quite a history of squeezing as many dollars out of its customers as its can. Since there is choice among PostgreSQL support companies, you'll never get into that position with it.

Scott Marlowe said...
Here's how PostgreSQL support has worked for me. I had a db last year that was throwing a panic error causing the db to restart midday and hence having a huge issue with a load spike each time it did this. Got a copy of the error from the error logs for one of the core developers and had a patch about 8 hours later.
It took me longer to wait til after hours to take the db down to apply the patch than it did to get it.
Anyone ever get a patch from a core developer from Oracle in < 24 hours from the time they reported it?
June 23, 2011 10:48 PM
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Mi wara wara said...
In past versions Oracle clearly had a lead in terms of performance speed and scalability. Nonetheless, PostgreSQL 8 may be just as good or better than Oracle in terms of performance speed. Likewise, PostgreSQL 9.2 may be just as good or better than Oracle in terms of scalability. When PostgreSQL 8 was launched, I remember reading posts that PostgreSQL actually beat Oracle in speed of certain types of operations, but they weren't allowed to post test results with Oracle, because the license prohibited it. In my opinion, the fact that Oracle prohibits independent reviewers from publishing performance tests is a good enough reason to not choose Oracle. What do they have to hide?
PostgreSQL version 9.1 does have pretty good support for clustering. See: http://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling