I can say though, that we never truly see the extent of either villains power. How powerful was Kuja before Trance? Could Kuja have had other devistating powers at his disposal during Trance?
Well, he did manage to not die while getting beaten up in order to achieve Trance. Other than that, he's feared because he has resources, and through manipulation and careful planning, more often than not, complete control of the situation.