...telepathy is an inborn trait vs. the claim that telepathy is a "calling" on Minbar.

I don't think it is "versus".
What is meant I believ is that those who are born as telepaths are led (by society) to see this as a calling, to which they will then dedicate their lives.
Says a lot about Minbari Society, IMHO, and not all good; quite in keeping with the tenets of a caste system, and also with some other observations made here recently.

BTW, did I hear a reference to *two* Minbari castes a few episodes ago, or was I dreaming that?