In my opinion the chief advantage of Everything is it is insanely customizable. By creating custom nodetypes you can do really complicated things which might be needed for a full content management system.

But it sounds like your users just want to drop something in and forget about it. In that case the simplicity of a wiki seems more attractive.

If I recall correctly, Everything requires a database while twiki doesn't. So backing up twiki is as simple as tarring up all the files and storing them elsewhere. It could even be done automatically out of cron

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