What do you do when someone trades a cow for information?
Baalberith uses his form mainly for the older crowd, and sometimes younger. It depends on what they are seeking from him. If they seek to trade talents or fate, family, anything that is material on some level, he will approach them with this form. This is one he uses when he is feeling almost fatherly.
Benjamin Province (Son of Johann)
This form is saved for people who have something he wishes, or that one of his master wishes. If they prefer men, he pulls this form out to attempt to seduce them to give their soul, drive them to murder, or blasphemy. For him, this is the one to convince people of things, seduce them, really. While the elder is to gain things from others.
Essentially the same idea of Benjamin, only for those that prefer women. ;)
In this form, he also acts as himself a good amount of the time.