Django

Django is the most mature of the Python web frameworks.  It has gained the reputation as one of the most well rounded starting points for websites and web services.  Out of the box it comes with support for PostgreSQL, MySQL, SQLite and Oracle databases via an ORM with native migrations.  Adding functionality is as simple as picking from any number of Python projects that are built to work with Django and add additional functions.  One of the best supported CMS projects is Mezzanine that gives you fully featured site Search functions, a Blog, SEO customizability, Social Media integration and Image asset management.

Django also comes with a built in Admin Panel that hooks into your project's data models and allows users to be given specific permissions and roles.  From this Admin system, people can add, edit and delete information quickly and securely.  This can allow something as complex as a CRM or HR system to be setup and customized in just days.

If you have specialized functionality you need, you can hook right into Python's advanced library of scientific and cutting edge open source projects.

Advantages

Django gives you a wealth of functionality right from the start and has a host of plugins that all bring in powerful features with little extra development effort.  This is most similar to the Ruby on Rails software stack that can quickly collect other plugins together to provide a feature rich product.

Django's foundation on Python means it is more secure, and has access to more security features, out of the box than other web frameworks built on PHP.  

Risks

Django is well designed and suited to specific tasks.  Trying to add functionality that fights with it's native layout can start to conflict with the large framework and ORM it is built on.  It takes experienced developers, familiar with Django's strengths and weaknesses to craft functionality that works with Django seamlessly.

Django's ORM is not well suited for all data management or reporting tasks.  You may need custom work done to efficiently optimize your database to support reports that touch large numbers of tables and rows.  A page that runs quickly at first can quickly start to take minutes or even hours to run if it has not been well designed.

Specialized NoSQL databases and caching utilties like Cassandra and Redis can help solve these performance problems with the need to redesign large amounts of your project.

Parthenon has helped a number of companies optimize Django projects that have started to run slowly, and needed more advanced processing done on data recorded over years of use.