[virtujoel]

>I suppose accessibility can be considered "features", but I'm strongly suspecting that the overcomplex button has worse accessibility.

Accessibility is incredibly hard to get right, particularly managing screen reader announcements, focus management and form validation. I recently had to build a website that met WCAG 2.1 requirements and it was made significantly easier by using React Aria (https://react-aria.adobe.com/) which is a similarly complex headless component library. To get an idea of the work that goes into making an accessible component, see their blog post about making a combo box where they test 4 different screen readers x 4 different browsers: https://react-aria.adobe.com/blog/building-a-combobox

(I haven't used Radix so I'm unsure how well they do a11y)