Answer:
   
   The real question is how one observes Yahrzeits that occur in the
   Jewish month of Adar: are they observed in Adar I or Adar II? Many
   issues in halachah are subject to debate, and this is one of them. The
   Sepharadic ruling (followed also by some Chassidic groups) is to
   observe in Adar II. Once Purim is on Adar II (to make a "redemption
   season" of Purim and Passover), the "real Adar" is the 2nd Adar.
   
   The Ashkenazic ruling is based on the notion that one ought not pass
   up an opportunity to do a mitzvah. Therefore, the earliest possible
   definition of yahrzeit, Adar I, is used. There is a custom to say
   kaddish on both days. However, in terms of being the chazan, the other
   yahrzeit date gives no priority over someone whose parent actually
   died in a leap year and has an exact yahrzeit.