When comparing Orion vs Paper, the Slant community recommends Paper for most people. In the question“What are the best gtk3 themes?” Paper is ranked 19th while Orion is ranked 29th. The most important reason people chose Paper is:
The look of this theme is inspired by Material Design.
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Pros
Pro Plug-ins including Pixlr image editor
Pro Built for front-end development
Orion was developed specifically for front-end development, making it a strong option for front-end developers thanks to features like syntax validation with ESLint and HTML content assist.
Pro Eclipse-like UI
Orion is developed by Eclipse and shares a lot in common with the Eclipse IDE UI.
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.
Cons
Con No runtime environment
Does mostly do file editing, but without good project support, web terminal, build/runtime environment.
Con JavaScript only
Orion currently only supports JavaScript.
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.