Debating what should be the shape of different buttons and CTA's on my apps (both iOS & Android). The design guidelines of Google/Apple are tending toward the simple rectangle w/o rounded corners. Any recommendations/experience/research on usability on the topic?
Option 1: Go with rounded corners and give importance to affordance.
Some research suggests that rounded corners enhance information processing and draw our eyes to the center of the element.
The post here: How do rounded corners affect usability? gives a lot better understanding on why to choose them not just in software, but for hardware as well.
Google's project called web components has already given special consideration to button's affordance (notice the nice shadow that makes the buttons look like buttons) along with rounded corners which are already being implemented in Android applications.