IBM Rational System Architect is an enterprise architecture management platform, that enables the use of abstraction to preserve design intents and tribal memory, and to provide auditable evidence of conformance to policies.
If you have a budget or the need for a complex modeler or need diagram transformation to code or vice-versa, IBM Rational System Architect is the way to go. If you need few diagrams or don't need the complexity or don't have a budget, Bizagi or Star UML get the things done.