When comparing Zukitre vs Papirus, the Slant community recommends Papirus for most people. In the question“What are the best gtk3 themes?” Papirus is ranked 3rd while Zukitre is ranked 9th. The most important reason people chose Papirus is:
All icons look pleasing, especially with the Arc theme.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Designed to be flat with sharp corners
The design of Zukitre differs from Zukitwo in that there are fewer gradients and rounded corners. It is also designed to be more flat.
Pro Sharp, flat, and fresh
All icons look pleasing, especially with the Arc theme.
Pro Familiar
Used on Lubuntu and BunsenLabs, for example.
Pro Active development
Cons
Con Only supports the latest release of Gnome Shell and GTK
For Debian or Ubuntu users this theme will not work as it only supports the latest version of Gnome Shell and GTK.
Con Under GNU GPL3
This limits the use elsewhere.
Con Contrast issues / No border around icons
It makes the the fast and makes it simple to add more icons(since you can simply scale them) however the contrast is lost in some situations.
Con No Ideas
It just copies the icon-syle from a different system.
Con Just another material style copy
Con Lacks icon for backintime
Backintime tray icon doesn't display on the panel because Papirus lacks the icon.