Multi level encryption starting with a client side encryption layer, allowing true end to end encryption for password sharing, followed by SSL and storage encryption
Transparent public audit possibilities of the complete code. Security comes with correct encryption and not by hiding security flaws.
The possibility to host the server on your own grands you even better access control possibilities. In addition you are independent and do not have to rely on public services.
Trust No One
No one who's selling security software will tell you this. All software and hardware have security vulnerabilities. And even if you have an application that is secure, your data can still be stolen, because there are just too many pieces involved.
There are new flaws in the underlying OS or virtualization discovered every day.
Your network equipment like routers and switches from various manufactures may have issues right now.
How many administrators patch and update your systems? How many have made a mistake with one of the zillion configuration possibilities?
What happens if one of your administrators goes rogue?
PSONO keeps the necessary trust to a minimum.
Application and Database servers hold no sensitive unencrypted data.
Administrators have and will never have access to any unencrypted data.
True end-to-end encryption makes network / infrastructure trust irrelevant
The server application has no access to any unencrypted sensitive data.