Two biggest things:

1. PKDNS - We use your key as an actual domain name. This ends up giving you total control over your data and identity in ways that Nostr never could. (You can keep your key cold, for example). It also allows the system to scale while staying censorship-resistant. Nostr breaks at scale.

2. SSG - We index everything using a semantic social graph. This allows users to curate the web together, instead of rely on central algorithms.

These are both different forms of "discovery" which Nostr lacks. These two primitives change everything in deep ways, offering something strictly better.