Radix and shadcn-ui are two popular component libraries for React, differing in their approach to design, accessibility, and styling. Radix offers low-level, unstyled components, providing full control over styling and architecture, making it ideal for advanced use cases requiring high flexibility and customization. In contrast, shadcn-ui is built on top of Radix, offering styled, ready-to-use components, streamlining development with a cohesive design system. When deciding between the two libraries, consider factors like desired styling flexibility, the importance of a consistent design system, and accessibility requirements to align your priorities with each library's strengths.