I have been asked to present the reasoning behind our choice of CodeIgniter over Drupal for the OU player/ OU embed projects.
I will argue that the OU player project provides an ideal case study for why The Open University, including the central IT providing departments should not adopt a one-size-fits-all approach to the choice of information technologies. At present, I think they are in danger of doing this. You may also be interested in Juliette Culver's post, Why we moved from Drupal to CodeIgniter, and Will Wood's post, Agile Ballooning.
First, some background. CodeIgniter is a minimal model-view-controller PHP framework. It is open source, makes full use of the object-oriented programming paradigm, offers database abstraction, an ORM (object-relational-model) layer, and various extension mechanisms including libraries, hooks and helper functions. By default, templating/ views are implemented in PHP, though an alternative templating system such as Smarty could be plugged in. There are many third-party plugins available, and it is a simple matter to plugin other libraries, for example parts of the Zend framework. As a low level framework, its benefits are a shallow learning curve, the promotion of maintainable, well-structured code, small footprint, performance and flexibility (http://codeigniter.com).