Fwiw I've been using Signal as my primary communications channel along with email for the past few years. There's an outage once a year or so, but I can live with that. It just works--for voice calls, video calls, chat, groups, etc.

The real question here isn't about which system is technologically superior (though HN gravitates to that question), it's which one is technologically superior taking into account network effects. Briar and Session may be great, and I wish everyone used them, but at present at least where I live it'd be very tough going. Getting people to use Signal isn't all that hard, the network is pretty robust in my communities (university city).