The defenses in both cases can be quite different. For some people, a cheap Chromebook that you can wipe quickly plus 2FA gives great security, or using a modern (encrypted) phone with Signal. But what if you are, say, protesting against the construction of a new Google campus on top of your neighborhood? Then you'd don't want all your secret stuff on their infrastructure. Normally you assume everybody is playing fair, but it would be so easy for them to push out a malicious update to your phone to gather dirt on you.

If one has experience with AOSP and security, there seems to be a market for an open, secure phone. But I wonder how you'd keep the organized crime out, or at least keep plausible deniability to not get into trouble...