React JS is highlighted as a powerful tool for developing cross-browser compatible web applications due to its robust community support and integration with tools like Babel.js that help address compatibility issues. While React Native extends these capabilities to cross-platform applications, allowing developers to use the same JavaScript codebase for both iOS and Android by specifying platform-specific requirements, it still requires attention to cross-browser compatibility issues. React's unique DOM system, efficient memory management, and features like live reload and synthetic events contribute to its performance and ease of use. Despite its strengths, React faces competition from other frameworks like Angular, Vue, and Google's Flutter, reflecting the dynamic and uncertain landscape of web development technologies.