When comparing Paper vs adapta-gtk-theme, the Slant community recommends adapta-gtk-theme for most people. In the question“What are the best gtk3 themes?” adapta-gtk-theme is ranked 1st while Paper is ranked 19th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Flat and colorful design
The look of this theme is inspired by Material Design.
Pro Does total makeover of your computer
It's a complete theme, with custom icons, GTK, cursors, Gnome Shell.
Pro Real dark theme
Pro Follows the material design guidelines
Pro Easy installation on Ubuntu
sudo add-apt-repository ppa:tista/adapta
sudo apt-get update
sudo apt-get install adapta-gtk-theme
Pro Most complete theme
It styles every nook and cranny of the OS UI, even the ugly Java apps look beautiful using this theme.
Pro Ergonomic
Not only looks good, but really accelerates work on desktop.
Cons
Con There is jumpy behavior when switching from window to window
You can notice jumpy behavior when switching from a forefront window to window behind it. Both windows jump a little which can slightly disrupt normal working flow.