Main pro of signal is that it's normie friendly, has a good UI, has a notable user base already, and has optional discoverability, and optional privacy.

I like SimpleX a lot but it's got a high learning curve, a UX that is still early, and otherwise just isn't convenient for people you know IRL.

Might do it with privacy people but I feel like signal is the winner even if simplex in theory has better opsec.