I recently moved my blog from Jekyll to Pelican and wrote about it [1].
Functionally some of the differences I found are:
* Jekyll output directory structure has a one-to-one correspondence with its input. While Pelican tries to standardize it for you e.g. static files go to one folder.
* Pelican has built in support for theming. Jekyll makes no such distinction between your theme and content.
* Pelican has a much more modular architecture since it can supports multiple inputs like reStructuredText/Markdown and multiple outputs like PDF
Anecdotally, I found Jekyll to be a bit slower than Python for building my blog.
