Confusion understanding transient behaviour?
Robust means that your controller will be less affected by plant variations. For example, if your plant transfer function is a crude approximation, you should aim for a more robust controller. It is loosely related to the concept of robustness https://en.wikipedia.org/wiki/Robust_control

Aggressive means fast rise time. If your model is really accurate, your actuators strong an fast, you can aim for a fast rise time.