On Nostr I just spray and pray that a Relay will store my data and that other users will connect to one of the Relays that sotred my data. In Pubky my Keypair is a censorship resistant DNS record that tells users where I store my Data (PKDNS). This offers a guarantee that I have all of the data that a User published, that I get the newest published version (mutability is still a big pain point in Nostr as Relays don't always respect updates or might not pick up on them) and on top of this is much easier to scale to a much larger Userbase. While both systems will to a certain degree rely on certain centralized data aggregators, on Nostr most Data will end on a handful of Relays. In Pubky you're likely going to see Indexers aggregate the Data from many Homeservers to build your Social Graph. Replacing an index that malbehaves is a matter of seconds. Replacing a few centralized Relays that host most of the data is much harder at scale. Regarding pubky.app, which is basically the first pubky-core based social application, there are some cool features like tags available with many more on the Roadmap for this year.