aptitude is a terminal-based apt frontend with a number of useful features, including: a mutt-like syntax for matching packages in a flexible manner, dselect-like persistence of user actions, the ability to retrieve and display the Debian changelog of most packages, and extreme flexibility and customization.
License: Open Source
Aptitude is primarily a package manager focusing on installing and managing software packages with a user-friendly interface, while Update Manager is centered around automating updates for installed software, making it more focused on system maintenance. Aptitude offers more features for package management and dependency resolution, whereas Update Manager simplifies the process of keeping software up to date.