Advantages of PostgreSQL
An open-source SQL standard compliant RDBMS:
PostgreSQL is open-source and free, yet a very powerful relational database management system.
Strong community:
PostgreSQL is supported by a devoted and experienced community which can be accessed through knowledge-bases and Q&A sites 24/7 for free.
Strong third-party support:
Regardless of the extremely advanced features, PostgreSQL is adorned with many great and open-source third-party tools for designing, managing and using the management system.
Extensible:
It is possible to extend PostgreSQL programmatically with stored procedures, like an advanced RDBMS should be.
Objective:
PostgreSQL is not just a relational database management system but an objective one - with support for nesting, and more.
Disadvantages of PostgreSQL
Performance:
For simple read-heavy operations, PostgreSQL can be an over-kill and might appear less performant than the counterparts, such as MySQL.
Popularity:
Given the nature of this tool, it lacks behind in terms of popularity, despite the very large amount of deployments - which might affect how easy it might be possible to get support.
Hosting:
Due to above mentioned factors, it is harder to come by hosts or service providers that offer managed PostgreSQL instances.