Jest is a popular JavaScript testing framework built on top of Jasmine, offering features such as native support for mocking, snapshot feature, and parallel testing. It provides simplicity, broad framework support, strong documentation and community support, making it an ideal solution for simple JavaScript testing frameworks with advanced features. On the other hand, Vitest is a fast and modern unit testing framework that complements Vite, providing speed and simplicity. Its main advantage lies in its focus on speed, making it suitable for large-scale testing scenarios or projects where test speed is crucial. However, Jest's larger community and established ecosystem make it more accessible to developers who prefer extensive documentation and support.