If you have the choice to use anything then SimpleX is gold standard. Signal is excellent if the phone number requirement isn't a problem for you. We heavily recommend https://molly.im/ for Signal users. Provides many privacy and security features Signal misses.

Session is good but disappointed with the lack of PFS. We disagree with their stance that it is not important. Exploiting someone's device gives access to their current encryption keys but if there is PFS then it doesn't imply recovering all past messages. It's great that they're honest though.