I think the difference would become quickly apparent. To me the no-debate rule for DIRs doesn't make a lot of sense and needs rethinking.
I still haven't got a clear sense of what DIRs are really for. What, essentially, is their purpose?
The DIR's are set up for members of that specific religion to discuss topics between themselves and answer questions from people who not belong to that religion. They are essentially closed areas that outsiders are allowed to ask question in.
It allows Jews, for example, to discuss the the role of the Temple amongst ourselves without a Christian telling us that the Temple is obsolete due to Jesus or for us to answer a question about our prophets posed by a non-Jew without a Muslim interjecting that Mohammad was the final prophet.
Each religion with a significant population here (and quite a few with no population here) have a DIR set aside for them to use.
The majority of the forum is open to everyone and debate, questioning, challenging, and open discussion are both allowed and encouraged. The DIR's are spaces set aside for specific groups to converse without those things, and the Same-Faith Debate section is the place for us to argue amongst ourselves.