research question

I am contemplating over possible research questions.  I was thinking something maybe like Is Mephostophiles for or against Faustus selling his soul?  I was thinking this one because I think that is a huge issue in the play and in comes up in almost every scene.  Another question I was thinking was How is religion tied into the plot of Dr. Faustus?  This is a more broad question, but I was thinking Christianity and would explain where I think Faustus is against God and for what reason and is for God and for what reason.  I would really appreciate inpute, because I don't know which one to do. Thanks!!