What are the reasons for and against studying other religions?

When I studied Spanish, I better understood my native English language. I wondered if the same kind of thing can happen in the realm of religion. What are the pros and cons of studying other religions and their practices as a Buddhist? To be clear, I do mean "studying" (and not "practising") another religion's practices... not that answers about the pros and cons of "practising" another practice wouldn't be most welcome, I just assume that practising another practice would be too confusing. Maybe someone will give an answer that challenges this assumption - Metta