Another common alternative platform to Drupal is Ruby on Rails. We really don't have much to say about Ruby except that it is a framework moreso than a platform. There are some characteristically challenging web development tasks that are quite easy to do with Ruby, and there are others which are infinitely more complicated than they should be.
One big difference is the fact that Ruby lacks the refined data object model found in Drupal that ensures interoperability between various aspects of the system, such as adding new modules to modify the operations of others. Whereas Drupal offers a self-generating database schema for many modules and underlying components of the platform, Ruby on Rails emphasizes a design philosophy holding that simplification of code conventions leads to better outcomes. While this all sounds good in principle, we have found there are certain tasks that make adherance to this philosophy an ideal moreso than a practical goal and breaking free from these conventions when necessary a daunting task (especially when integrating with external systems).