When comparing Arc vs Iris, the Slant community recommends Arc for most people. In the question“What are the best gtk3 themes?” Arc is ranked 2nd while Iris is ranked 9th.
Ranked in these QuestionsQuestion Ranking
Pro Customizable to dark or light themes
Pro Has both GTK2 and GTK 3 support
Users will be able to match their gtk2 and gtk3 themes easily due to Ark supporting both.
Pro Supports gnome-shell
Pro Available firefox and chromium themes
There are matching themes for Firefox and Chromium for those that want to have a fully matched looking environment.
Pro Really clean and nice-looking
Pro Purchasable filters to heighten visibility in certain conditions
Iris has filters that can be purchased through in app purchases that allow for increased visibility in certain lighting situations.
Pro Easily turned on and off
Iris has a quick toggle in the notification drawer with allows for the user to easily turn on and off the function of the app.
Pro Puts an overlay of your camera feed on top of all other apps
By overlaying what the camera sees over any app on the device, users can see what is in front of them while still looking at their screen, retaining all the functionality of every app or game they use.
Con Bleak font colors that cause eye strain
The font color in Arc and Arc-Darker is not black, but lightgray
after prolonged usage, it becomes apparent that this font color, combined with white backgrounds causes too much eye strain
Con Has some contrast issues
The theme is a low contrast theme so it really depends on the screen brightness if you see borders or the text, some elements don't even have borders - this makes the theme barely usable for portable devices.