When comparing GitUp vs gitk, the Slant community recommends GitUp for most people. In the question“What are the best Git clients for macOS?” GitUp is ranked 8th while gitk is ranked 14th.
Ranked in these QuestionsQuestion Ranking
Pro Open Source, GPL-licensed
Pro Allows doing complex things without memorizing git
Git usage beyond basic checkout/commit is arcane; GitUp lets you do things in git in seconds that would take you a half hour of research with the command line.
Pro Full undo
You can backup, or edit commits, if you make a mistake.
Pro Blazing fast
Fast Git GUI. Everything is already there and loaded when you open up the window.
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
Since it's pretty minimalistic and does not contain a lot of features (for example, it can't commit), it's quite fast.
Gitk is a free and open source tool. It forms part of the official git suite.
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.
Con OS X Only
Only available for OSX, so if you are used to working with different OSes and you want the same tools in each of them, it's impossible to have that with GitUp.
Con Font size is not adjustable
Tiny font not good for those with poor vision.
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.