To get people to leave Telegram or WhatsApp I think Signal is best. Has Stories, Stickers, etc. Features people who don't care my about the tech expect to have. Largest userbase of the three I assume so biggest network effect.

SimpleX seems nice too but the link exchange to add contacts could be a entry barrier. Less features than Signal at the moment.

Haven't tried Keet yet. One doesn't hear much about it though so I suppose the userbase is the smallest. Tough sell 😄