I think this is a reasonable analysis. I would refine it this way (examples are only for illustrative purposes):
Tier 1 secure messengers: all possible tradeoffs in favor of security made; use for worst-case adversaries:
- Signal/TextSecure
- Pond
- PGP†
- OTR
Tier 2 secure messengers: serious secure messaging protocols that make some tradeoffs in favor of adoption and usability; use for normal messages of low sensitivity:
- WhatsApp
- iMessage
Tier 3 secure messengers: secure messaging protocols with flaws, limited cryptanalysis, only content-controlled browser clients, &c
- Redacted to avoid flamewars.
Everything else: insecure; use only to bootstrap conversations to a Tier 2 protocol (knowing that if you're a state-level target, you're exposed even after you "upgrade")
- Google Talk
- Facebook Messenger
- AIM
I think WhatsApp would like to be a tier 1 secure messenger (they'd be the first mainstream tier 1 secure messenger!) and they have a shot at being that, but they're probably some years away from it.
† (I know PGP and OTR are cryptographically limited compared to Signal Protocol, but from an OPSEC perspective they're still a tier above iMessage.)
Tier 1 secure messengers: all possible tradeoffs in favor of security made; use for worst-case adversaries:
- Signal/TextSecure - Pond - PGP† - OTR
Tier 2 secure messengers: serious secure messaging protocols that make some tradeoffs in favor of adoption and usability; use for normal messages of low sensitivity:
- WhatsApp - iMessage
Tier 3 secure messengers: secure messaging protocols with flaws, limited cryptanalysis, only content-controlled browser clients, &c
- Redacted to avoid flamewars.
Everything else: insecure; use only to bootstrap conversations to a Tier 2 protocol (knowing that if you're a state-level target, you're exposed even after you "upgrade")
- Google Talk - Facebook Messenger - AIM
I think WhatsApp would like to be a tier 1 secure messenger (they'd be the first mainstream tier 1 secure messenger!) and they have a shot at being that, but they're probably some years away from it.
† (I know PGP and OTR are cryptographically limited compared to Signal Protocol, but from an OPSEC perspective they're still a tier above iMessage.)