This might be of interest here: https://theintercept.com/2016/06/22/battle-of-the-secure-messaging-apps-how-signal-beats-whatsapp/.
I think the key points of Signal are the same compared to whatsapp: Signal uses always E2E encryption, it collects no metadata at all (Google only sees the time you communicate but not with whom, since the official version of Signal makes use of GCM for push notification), no unencrypted backups or anything.
When you keep in mind that Google and Facebook (Whatsapp) make money with your data it is completely understandable why they will always try to get as much as possible of it. That’s why I always prefer Signal because they simply have another business model and won’t try to circumvent your security at any point. Of course the big companies try to look as secure as possible (they use Signal E2E encryption), but in my point of view this is only “greenwashing”.