I think this discussion should also mention that Signal is a non-profit organization, dedicated to enabling secure and private communications.
Yes, it s not strong proof, but it should be taken into account when comparing the goals and motivations of organizations developing various other communicators.
The organization behind your communicator app could be in the business of gathering data about you and selling it in various forms (Facebook, Google), in the business of selling hardware and add-on software services (Apple), or in the non-business of trying to provide you with private communications. I prefer to look at the history of who founded and continues to run the Signal Foundation. Moxie Marlinspike. Moxie has a long history of improving security in all kinds of tech and fighting for privacy.