Good idea David, hopefully the outcome of this thread will be very useful in helping to educate. My understanding on some of the some of the major differences between the tech, it would be great if others could chime in to confirm these and help build the picture.
Freenet is intended as a network for public sharing and broadcast of files and is not intended to limit access to those files. Therefore, it is not used for private storage of data and does not permit ‘ownership’ of data in the same way that users can (will) with the SAFE network, which permits both public and private data. AFAIK, Freenet also removes data which is not commonly accessed to save space, I don’t think there are any deduplication mechanism in place.
I also believe that GNUnet is similar in this regard, not allowing users to control, edit or delete data.
We also get compared to Tahoe a lot, as I see it the major differences here are that Tahoe does not; preserve the anonymity of uploaders or downloaders and is also not a reputation based network.
I hope this info helps!