If I use the verifyEqual built-in keyword, it seems I lose the possibility to provide a customized assertion-failure-message. In my above example the assertion failure is quite straight forward, but in others that message can very much help the debugging effort. I do agree that continue-on-failure is something I lack with the current Groovy assert keyword.
Update: I did find this topic JUnit-like assertion method that can emit custom message for a custom keyword that provides best of both worlds!