Personally, I think have it all together is better. Why? Think about it. Why have more room on your homepage for more shit to load for the admins and/or super mods or anyone else for that matter that don't know how to set up forum permissions? An open forum shows that you don't care about how many members you have, it just shows you care about the sharing. Yes, it is a lot of work to make sure the thread stays clean and such but other members can post replies in regards to the download with comments like if it worked or if it didn't work, etc. When I ran ShareDXS, we had everything open and I ONLY submitted stuff by my uploaders or something that had ShareDXS.com in the filename and/or as the password. I did submit other stuff too here and there but most of it was uploaded by staff or someone for ShareDXS itself.
Now...why close it down and have a guest section? Think about it...if you have an open forum and your forum gets A LOT of visits - especially from google...google will compound all the links and store them and raise you higher in the search results. When you know that you can be stable without Katz anymore and still grow on bigger or if you just e-mail Katz and tell them to wipe your submissions clean so you can start over (so you can close the section to members only). You then make a guest section and submit that content...but everyone else from google, they are continuously coming to your website...if they REALLY want to view that thread that bad, they will sign up and look at the thread...meaning more members. In the long run, you will have WAY more members than you would have gotta from a DDL site.
People from a DDL site (most) just go on a site, download what they want, and leave. But people from google go and see a thread to members only, 50% chance they will sign up and about 50% of those people will be active users.
So yeah, open forum for a good amount of time, then close it when you're big enough and submit from a guest section later.