By which I mean in terms of usage, development, or stability. Also along those lines, which English-speaking instances would you recommend?
Interested as Misskey & forks have some feature edges over Mastodon in my opinion, but it’s somewhat harder to find discussion/info about them.
Can’t say much about the other forks, but Sharkey seems quite nice. Also, they recently developed a nice XMPP account integration for it, but it would probably also work with other forks.