I think it may be best to make all hardware and software buttons and elements slightly rounded squares and rectangles instead of circles or pill shaped stadiums, except for uncommon elements with a specific purpose like circular dials or gauges.
What
- Circles or round images may be better for looking at or more pleasing to the eye for untouchable objects, and can make some of the better looking logos or icons, which can be used within certain buttons or key elements to label some of them with a pleasing image
- Slightly rounded squares and rectangles may be better for encapsulating information and selecting items or touchable objects within practically all user interface elements such as buttons, keys, menu items, tabs, dropdowns, search boxes, etcetera
Why
- Most importantly, slightly rounded squares and rectangles are better shapes for clicking easily and efficiently using any input method, including precise ones like a mouse cursor
- They more accurately portray their clickable area and economically take up more usable surface area available to them, making them quicker to navigate with less missed clicks
- They fit together and look more natural next to each other while also resulting in less wasted space between them, or even no wasted space when connected with a thin line
- They more naturally and adequately fit various content like text and images of all shapes within their boundaries, allowing content to be larger and show more than in a circle
- They match each other better since all are similarly shaped, as well as the surrounding elements including boxes, panels, windows, or borders which cannot be circles or pills
- They are uniform objects with four equal corners, which are pleasing to the eye and natural looking as buttons or any other elements within the overall user interface