AtMonitor is an advanced monitoring tool for Mac OS X that displays system activity in real-time. Developed by atPurpose Technologies
License: Free
htop is a terminal-based process viewer and manager, ideal for users who prefer a lightweight and customizable interface, while Atmonitor offers a user-friendly graphical interface with detailed monitoring features, making it more suitable for users who need multi-user support and alerts. The choice between the two depends on whether the user prioritizes a command-line tool or a graphical monitoring solution.