Bluesky is a different protocol than Mastodon, but conceptually I think it's fair to say they're similar.

I think Bluesky would clean up if it could also interop with Mastodon - people want to leave Twitter but it sucks having to choose between Mastodon and Bluesky and so I think some folks are just in a holding pattern waiting to see what wins. Bluesky feels more like Twitter so I think it would get a lot of folks, but I think people hesitate to bet on it just yet.