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?
(I know I said I'd stop responding in this thread, but since this is a direct question to me I'm going to say how I see it.)
Originally when I joined RF, I didn't see the value in DIRs, since there are rarely times I think it's ok for me to post in them. I later saw DIRs differently, after being a Moderator.
This is my understanding of the situation. It is possible it differs from the current staff perspective:
I think RF has the bases pretty well covered for types of debates and discussions, so I see it mostly as a matter of where one is posting, not whether or not one gets to have the types of discussion one might want.
Most of the forum is open for debate, so anything one might want to debate that is discussed in a DIR can be discussed in a debate thread.
However, (I think this is often the crux of the issue when someone is bothered by DIR rules) one may not force someone else into a debate the person did not agree to. This can feel frustrating at times.
One can't quote someone from a DIR discussion and attempt to discredit their statements or demand they back it up in a debate. But, one can begin a debate on the general topic in the Religious Debates section -- without appearing to be calling out that other member. There is nothing about RF rules that obligates another member to participate in a debate, if all they wish to do is participate in discussions -- so there's no guarantee the parties of a DIR conversation will want to participate in some one else's debate thread on the same, or similar, subject. We have members here who express their sole interest in being here is for discussions with like-minded people, and that they have no interest in debate on their beliefs. To allow debate in DIRs would drive those members away and, IMO, cut a huge chunk out of what I understand to be valuable about RF.
My understanding of the purpose of the DIRs is (as a safe space) and mainly to function along the same lines as a church, temple, meeting place of that group -- for people around the world to have a get-together location, where they don't have to back up their beliefs for outsiders, and can simply discuss the details of those beliefs.
I think of it like a long street with churches, temples, mosques, meeting places where one may observe the conversations of different groups. The objections and opinions of outsiders have no place there. I think it's a social faux pas to attempt to debate in a DIR, similar behavior to:
1. A Christian going into an Atheists group meeting, and attempting to preach and save souls.
2. An Atheist interrupting a church meeting with demands for proof of God, and challenging the theology.
It's just an inappropriate place for those sorts of things. One may ask respectful questions, but if the intent is not really respectful, common courtesy would require that one keep one's mouth shut.