That is an impossible question to give one answer to. There are lots of considerations. For example: 1) Do you trust facebook with messaging metadata? For exam

That is an impossible question to give one answer to. There are lots of considerations. For example: 1) Do you trust facebook with messaging metadata? For example, do you want them to know that you messaged your friend Jane a specific number of times on specific dates, knowing that they can coorelate this information to facebook profiles, and will give up this information for ad, and law enforcement purposes. 2) Do you trust Signal's infrastructure to be reliable when you need it? 3) What is you're threat model? For me, I want to be kept out of all ad-related data sets, and I want to have conversations with friends without having to think about a paper trail. 4) Do you care that you will have to convince people to install yet another messaging app? 5) Do you trust that Signal and WhatsApp have correctly integrated the underlying crypto protocol? I assume that you would, considering its history. Still, I would trust signal more in this regard. 6) Do you think that Facebook or Signal is more likely to cut a privacy corner in support of a ease-of-use feature? Do you care? For my friends, the answer is that I use signal. Everyone who doesn't use signal falls back to getting SMS, or phone calls. The problem here is that SMS and phone calls are both huge privacy holes. For my threat model, I don't care, but you might.