If you don't mind a learning curve and having to use the Web interface (because there's no native mobile app): (streams). From Friendica's creator.
If (streams) sounds good, but you need a shit-ton of extra features on top (and be it diaspora* connectivity), and you don't mind an even steeper learning curve: Hubzilla. Also made by the guy who made Friendica.
If you absolutely, absolutely, absolutely must have a dedicated native app on your phone, you're on Android, and you can live without features such as nomadic identity, multiple channels per account and advanced, fine-grained permission control: Friendica.
If you absolutely, absolutely, absolutely must have a dedicated native app on your phone, but you're on iOS: Wait for Relatica to have a stable release, then Friendica. (Caveats see above.)
Forget diaspora*. It's fading out. Shortly before New Year's Eve, a bunch of big diaspora* pods shut down, and at least according to one stats site, diaspora* lost more than haf its users.
And Pleroma is a Twitter replacement that, just like Mastodon, started out as an alternative UI for GNU social.