> Self-hosting is clearly inferior in major objective measures: availability, durability, and security.

I'd not go as far. You can have your setup behind a VPN on a high port, go for distributed storage (for example at your home and at your parents) and be rather secure with a stable, auto-updated distribution. Cold backups could be an encrypted blob in a cloud or a tape somewhere.

Now, of course this needs quite some upfront investment in time and money; without a solid setup, I fully agree that the cloud is superior (unless your prefer your data lost over read by the NSA).

Other than that, it mostly boils down to risk management: A third-party hacker might have an easier time with your network than Google or Dropbox, but being script-kiddie save is not that hard [0], so it needs to be someone with time and skill. TLAs can't simply subpoena your data, so it might be harder for them - unless your home network is setup badly [1] or they're willing to possibly burn a zero-day. Your day-to-day ad agency is not going to lay hands on your data. It really boils down to what aspect you optimize for; given the grandparent, I assumed it to be privacy and therefore selfhosting to be probably better. But I should've been clearer on that :)

[0] Yes, mistakes happen, but big corporations have also been hacked with trivial exploits, so let's call it even.

[1] This also poses a danger to your login data, though, so the Cloud security team does not help either.

Not so.

Availability: Raspberry Pi plus USB battery pack is more available than the Internet, since when my home power's down my Internet connection goes.

Durability: Have you ever heard of a Raspberry Pi dying?

Security:

  sudo apt install unattended-upgrades
  echo "0 4 * * * reboot" | sudo tee -a /etc/crontab

And all the functionality's available through Nextcloud. It's easier to set up than a Facebook account, and easier to maintain than a Google account.

This is assuming you don’t leave home. If you travel a lot, self-hosting on your residential internet connection is not going to be a very good experience.

When your house burns down?

Your house is less likely to burn down than Google is to cancel a service you use.