When comparing adapta-gtk-theme vs Materia, 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 Materia is ranked 5th.
Ranked in these QuestionsQuestion Ranking
Pro Follows the material design guidelines
Pro Real dark theme
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.
Not only looks good, but really accelerates work on desktop.
Pro Customizable via Oomox app
Users can build completely personal version easily using Oomox Gui app.
Pro Under continuous active development
Responsive and helpful developer.
Pro Good support for various DEs
Includes support for Gnome Shell, has a Cinnamon desktop theme, plus supports XFCE, Mate and all the usual suspects.