There is a qualitative difference between them.  Mindfulness is a necessary condition for insight.  When we practice mindfulness meditation we create a momentary refuge from the ordinary consciousness of craving and aversion. In this state, first we gain insight into our personality, and later we gain insight into how we adhere to the appearance of permanence and solidity.  Insight meditation assists us to access the nature of suffering, change and the absence of self (dukka, anicca and annata).