I’ve often wondered why people seem to prefer either MySQL or PostgreSQL. For the most part, I think it comes down to the following:

• Familiarity.
• Friends (a.k.a. support system) being more familiar with one over the other.
• Ease of getting started. Most web hosting providers support MySQL out-of-the box.
• Name recognition.
• Ease of support.

Here are some resources that could be useful for learning the pros and cons of each database:

• What MySQL can learn from PostgreSQL
• What can PostgreSQL learn from MySQL and the accompanying presentation
• MySQL quirks and limitations
• Why PostgreSQL?