Skylark is optimized for Outernet and librarian is not longer supported. So no bugs will be fixed and new features will not be implemented.
Outernet will shift to a new type of Signal as far as i know, so it could be that librarian will not work anymore after that.
You can also navigate better trough the data (like News etc.) in Skylark because the interface is way better.
I would just use the Rpi image as long as it works