 CONT: Potara Earring fusion is inconsistent throughout the series.  Goku and Vegeta create Vegito, a perfect mix of the two fighters in  which neither is dominant over the others. Yet with the Supreme Kais  its a totally different story. When Elder Kai fused with the witch,  he is clearly the dominant personality. Same thing when Supreme Kai  fuses with Kibito, Supreme Kai is clearly dominant in personality.