As I noted, if the IETF publishes IDs, why bother with RFCs?
It's difficult to imagine that you mean that as a serious question, but just in case:
You are asking whether there is an important difference between a circulating mechanism that has no review, approval or quality control processes, versus one that has all of those vetting and refinement attributes?
And by the way, formally, I-D's are not "published". That's a semantic point, but apparently it's important for this discussion.
d/ -- Dave Crocker Brandenburg InternetWorking bbiw.net