Visual Paradigm (VP-UML) is a UML CASE Tool. Developed by Visual Paradigm International
License: Commercial
Apps available for Mac OS X Windows Linux
UMLet is an open-source Java-based UML tool designed for teaching the Unified Modeling Language and for quickly creating UML diagrams.
License: Open Source
Visual Paradigm offers a comprehensive suite of modeling tools and is better suited for complex projects requiring collaboration, while UMLet is a lightweight, open-source tool ideal for quick UML diagramming and simpler projects.