My understanding of MongoDB is that it's another variety of a NoSQL database. MongoDB uses JSON (a little like XML), and I think it has a facility to store files/binaries, but any of the features of CMOD that make it an incredible report management system are absent. MongoDB also isn't content-aware, so it can't automatically index AFP, Line Data, or PDFs, nor does it have the ability to parse and compress data.
In short, there is no comparison, unless you want to consider investing millions of dollars building an Enterprise Report Management product around it.
-JD.
