Let's Chat is a persistent messaging application that runs on Node.js and MongoDB. It's designed to be easily deployable and fits well with small, intimate teams.
License: Open Source
Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with users of a different service provider via online chat, Voice over IP, and Videotelephony. Developed by Matrix.org
License: Open Source
Matrix.org offers a robust platform with advanced features such as end-to-end encryption and large group support, making it suitable for organizations with high security needs. In contrast, Let's Chat is a simpler solution ideal for small teams, focusing on ease of use but lacking advanced features like encryption and video conferencing.