I know everyone else in the west seems to use WhatsApp but in my social circle I connect to nearly everyone via FB Messenger. I have but don't use WhatsApp. I have no idea what it provides that FB Messenger doesn't provide and better. I don't need a phone number for FB Messenger. I can access it trivially at messenger.com, no need for the crazy QR code non-sense of WhatsApp. I also do not have to give FB Messenger access to my contact list, unlike WhatsApp (maybe that's changed but it used to be required).