UIkit provides a well-documented API and a wide range of pre-built components, making it easy for developers to quickly build UIs. JSS, on the other hand, requires a deeper understanding of CSS-in-JS concepts and may have a steeper learning curve for developers who are not familiar with this approach.
Community and Support
UIkit has a large and active community with regular updates and ongoing development. It has extensive documentation, tutorials, and community resources available. JSS, while not as widely known, also has an active community and provides documentation and examples to help developers get started.