Please read the and papers yourself to make an actually informed decision. I find most normies look at signal or WhatsApp. Whatsapp is more mainstream (they run ads everywhere including televison). If your choice is between signal or whatsapp please convince them to consider signal. Both can be a trust-me bro model but one is owned by a company who has absolutely no incentive or history at preserving user's privacy, in fact their business model relies on the complete opposite.