Five+ years from now, you are hired to support and extend a data-centric web application written in Python that hasn't been kept up to date. Would you rather prefer it was written in the current version of Django/Pylons at the time, using the available standard components, or kept minimal with something like CherryPy/web.py and a few library dependencies?

Heavy framework

Advantages:

• standard approach to application design and structure, as encouraged by framework;
• less application code to worry about.

Disadvantages:

• requires learning the framework to understand how things work;
• broken things in old version of framework difficult to fix;
• upgrading to new version potentially difficult due to changing APIs;
• finding relevant documentation/help potentially difficult due to changing APIs.

Light framework

Advantages:

• most application code is directly "visible";
• only needed features are implemented;
• architecture should be simpler to understand;
• less need to upgrade external dependencies;
• easier to upgrade external dependencies.

Disadvantages:

• some reinventing the wheel;
• non-standard design and structure (with the associated unique issues and bugs).

I will update the list with any helpful answers.