In his appearances in the classic He-Man cartoon, Granymer came across as more powerful than any other being on Eternia. He easily defeated He-Man. However, He-Man taught him some lessons in morals, and Granymer went from the typical arrogant dragon to a more good natured being. Certainly, he had become a force for good on Eternia.
In their shared appearances in the She-Ra cartoon, Hordak was downright snivelling in Horde Prime's presence. Clearly, Horde Prime could have defeated Hordak just as easily as Granymer had defeated He-Man.
So... who would win the one-on-one fight between the most powerful force of good on Eternia, and the most powerful force of evil from She-Ra's show?