Signal is the best.

The thing it’s missing the most is better multi device support and an updated desktop client.

For me, I think Matrix is more complete (specially since it backs-up your chats and media encrypted). The only thing it’s lacking (at least Element specific) is encrypted chat search support on mobile.

Yeah, it sucks that if I were using Signal only on my phone and eventually decide to start using it on desktop, it doesn’t sync any conversation history, resulting in the desktop client showing nothing from before you set it up.