TESTARE should be used by JAVA software developers who need to write unit and integration tests for distributed applications, and as such need to perform in container testing.
If all you need to do is writing simple unit tests for client side code, if your business logic stays contained in just one single JVM, then there is no good reason to move away from JUNIT. In this case TESTARE cannot do anything for you that JUNIT doesn't already do. Except maybe if in the future your now simple application will grow into a distributed one, using TESTARE will enable you to easily scale your tests collection to the distributed environment.
If you get into distributed computing from the beginning, with multiple execution scenarios and distributed data configurations, TESTARE offers you important advantages over JUNIT is terms of test case development speed and maintainability, as it offers scenario based test case distribution automation and enables you to write test cases in a manner that is independent of where the test or its decorators will be executed.