Hanging leg raises are a staple in Convict Conditioning and progressive calisthenics. They are certainly one of the best core exercises by far.
The dip bar leg raise is the second cousin to the hanging variety and it offers some unique challenges. It requires more shoulder and back stability, plus it can engage your pushing chain more than the hanging leg raise.
All of this can make dip bar leg raises a valuable tool in your core training workout. Check out the details in this video: