Since some people have asked me, here's a quick thread on initial experience comparison between Bluesky and the fediverse. It's important to note that this comparison is somewhat absurd by default because Bluesky is still tiny & unproven, but there's interest so I'm happy to share what I've observed. Also, I don't get into protocol differences because honestly who cares. So:

The fediverse (including Mastodon) is better at: having been proven to scale, having multiple places running different services, offering more choice of apps, giving a choice of legal jurisdictions and business/non-profit models, and is still growing far faster, especially globally.

Bluesky is better at: Onboarding & signup experience, having fewer choices to make, quality of the default app, familiarity for people used to Twitter's design, discovery of other users within the existing service.

Here are things we don't know: What Bluesky's trust, safety & abuse policies will look like at scale, compared to fediverse services. Mastodon and other fediverse services have been uneven at times, but have matured over years; Bluesky is still tiny and hasn't been tested at all. We don't know if Bluesky can scale, either technically or socially.
There are also platform features that people might legitimately have different goals for. Bluesky makes content & people searchable by default, which Mastodon only does for hashtagged content. This aids discovery, but can also enable kinds of abuse. Fediverse partisans argue this constraint helps build healthy community, but many newer users find it a frustrating omission. Both platforms let you use your own domain, but it's much harder to do so on the fediverse right now.
People's perception of the overall fediverse is (probably unfairly) shaped by Mastodon, though many other services make different choices around key features that others might find meaningful. Understanding federation is a huge barrier for people who just want to (re)connect with friends or institutions. People's perception of Bluesky is shaped by Jack Dorsey's role in its initial conception; we don't yet know whether that's fair, though he doesn't seem very involved at all.
My feeling, which I expect will encounter some resistance for a while, is that if Bluesky succeeds (for whatever definition of "success"), it's just part of the fediverse. Email has thrived for a long time with multiple protocols making it run behind the scenes; there's no reason that the new wave of social networks built on the open web can't share that trait.

@anildash My strong suspicion is that Bluesky (or any similar corporate product that preaches federation) will use federation for their initial growth spurt, and then find a way to pull up the drawbridge once private equity or the Saudis decide that lock-in sounds more profitable.

I don't know why I would be so cynical, except for my lying eyes and the entire history of Facebook, Twitter, Google, YouTube, RSS, XMPP, OpenID, and even Open Graph meta tags.

@jwz @anildash Deep cut with xmpp.