I'm oscillating between the two, myself. I find django more verbose than it needs to be and as the number of the applications grows in your project you'll be switching between files with the same name till your finger (or mouse) hurts.
Web2py on the other hand has a poorer documentation and it does not have a administration interface customizable for the client. I'm also not sure about how well it scales outside of Google AppEngine. This frase taken from the documentation: "Even if there are multiple web servers, there must be one, and only one, database server. " worries me a bit. Apart from that I did not found any downsides for web2py. In my experience most of addons that I used in django was to supplement django's own deficencies as a webframework and not to add extra functionality to my applications. The top apps at http://djangopackages.com/categories/apps/ support my conclusion.
