When comparing Ungit vs gitk, the Slant community recommends Ungit for most people. In the question“What are the best Git clients for Windows?” Ungit is ranked 21st while gitk is ranked 26th. The most important reason people chose Ungit is:
Ungit is open source software available under the MIT Licence.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Free and Open Source Software
Ungit is open source software available under the MIT Licence.

Pro Cross-platform
Works on Windows, Linux, and OS X.
Pro Optional Integration with Modern Text Editors
Ungit can be integrated directly into modern text editors, Atom, Brackets, and VS Code.
Pro Web-based interface
Ungit is web-based, meaning you can run it on your cloud/pure shell machine and then use the UI from your browser.
Pro Visibly more compact overview output than many other options
When using gitk to scan a long list of changes, the user is able to see more of the list without pagination, as there is no huge buffer of whitespace between each entry.
Pro Fast
Since it's pretty minimalistic and does not contain a lot of features (for example, it can't commit), it's quite fast.
Pro Free
Gitk is a free and open source tool. It forms part of the official git suite.
Pro Comes with Git
Gitk is a part of the git package, so no additional application is necessary: it is developed right alongside git itself.
Pro Easy to use
Cons
Con Node.js dependent

Con Setup is not user-friendly
Ungit is distributed as an NPM package and requires git and Node.js to be installed on your system before you can run it. Ungit must be launched by running ungit
in a command line terminal.
Con Exposes git commands to your network
No authentication, if someone can communicate with your computer on the port this is running on, they can execute any git command they want on your repos as well as view your filesystem's folders.
Con Cannot commit
The user needs to use a different Git client (GUI or otherwise) to commit changes.
Con Does not automatically update
The user must press F5 to refresh the view as there is no automatic update available.
