Related : Corey Doctrow's article (again) about how he doesn't trust Bluesky enough to move there from mastodon. Especially Bluesky's promise to allow users to migrate to another host in the fediverse. https://doctorow.medium.com/https-pluralistic-net-2024-11-02... Older article : https://pluralistic.net/2023/08/06/fool-me-twice-we-dont-get...
I'm not sure this is up to date, but Bluesky/AT Proto's architecture is pretty complex to wrap my head around so maybe I just misunderstand. The biggest difference is that unlike Mastodon, Bluesky doesn't really have a single concept of an 'instance' that represents an independent segment of the network like Mastodon does. Instead you have PDSs (which is a user and their data), relays (which centrally relay multiple PDSs like a firehose), and the app view (the frontend for visualising the relay and interacting with PDSs).
You can host your own PDS so you are in control of your own data and identity, and you can migrate away from Bluesky-operated PDS to your own, though at the moment you can't migrate back https://github.com/bluesky-social/pds/blob/main/ACCOUNT_MIGR... https://whtwnd.com/bnewbold.net/3l5ii332pf32u
Bluesky's AT Proto design has different trade offs to Mastodon. Bluesky seems like the more feature complete, technically superior, twitter-scale design, being expectedly more complex. Mastodon/ActivityPub is easier to boot up something completely decentralised, but hosters often complain about scale. The real test comes down to the resiliancy of the service is the main provider shuts down. At the moment I think Bluesky would suffer a lot more than Mastodon if the company just went away.