Marketing would suggest that the commercial versions of PostgreSQL are somehow objectively superior to the Open Source versions of PostgreSQL. In reality, this is not the case. When deciding what version of PostgreSQL you are going to run, you need only be aware of your own needs.
For example, are you going to need installation support? Is a graphical installation important to you? If they are, then you should probably purchase a commercial version of PostgreSQL. However, if you or one of your staff are comfortable with compiling and configuring source code, the Open Source version could be more applicable to you.
There are two additional questions you may want to ask. Do you wish printed documentation and are you willing to pay for PostgreSQL? Both of the commercial distributions come with printed documentation. However, if you are currently reading this book, we hope you may not need the additional documentation. The other question relates to cost. Great Bridge PostgreSQL, as of August 2001, is priced at 495.00 USD. The Red Hat Database is priced at 2,295.00 USD.
The most important thing to remember when deciding on which version of PostgreSQL to use is this, from a perspective of general usage and feature availability, there is no practical difference between the Open Source versions, and the Commercial versions.