Signal has the worst app (on iOS) and worst UX of anything I regularly use. There's unlikely to be a desktop client which is actually usable (doesn't depend on a phone, works on platforms I care about). The app is less buggy on iOS than it used to be, but it's still not great. Also doesn't work well with groups. And tied to PSTN identities, and the "talk to a new person on the street" interaction sucks. But, the most widely audited crypto, a good development model, and good adoption within some activist communities.
Wire is great, although it's a little "game-like" vs. professional for certain UX. I know the developers and really like it, and it's great for group chat and desktop, but doesn't have much adoption. But, one big global system, too.
Riot/Matrix and Mattermost are nice because you can run them on private networks. Nice apps. I've not seen as much analysis of their security as Signal.
Whatsapp, Telegram, etc. have massive adoption. Whatsapp is now solid security for user to user.
Apple's stuff is great but is Apple-only, and I'm wary, even if I trust the security model, to let a single company own my OS (and update whenever, without really auditing it) and my "end to end encrypted" apps -- way too easy to slip in any kind of backdoor there if they want.
etc. I'd happily trade in 50 ok to good systems for one great standard and then OS/other-application integration -- but it seems like we don't do standards anymore.