@_elena Very brief summary on that: In Hubzilla, you have your posts and communication living in a channel that can have multiple clones on different instances. So in case you lose access to your main instance (because it goes down or is discontinued or the admin decides to block you), you still have access to your history in there. In Mastodon or even Friendica, such a scenario would completely strip you of all your previous data as even though you can export your full history manually, you can't re-import this anywhere except for the contacts. In some systems like pixelfed, not even a full data export is possible. Not sure whether this is an individual requirement of mine but it feels very difficult from an "own your data" perspective. On Mastodon, there's a change request - github.com/mastodon/mastodon/i… - for that which hasn't been implemented yet.
cc @chris and @jupiter_rowland who know the Hubzilla details much better than I do. (Mostly Friendica/micro.blog user here.)