I don't know about the community. But from a protocol standpoint I think Nostr might actually be technically better.

At a high level, ActivityPub (and it's implementations) imply there are many servers and to operate in a federated way, each server needs bidirectional communication. This is results in a exponential increase in traffic between servers and storage requirements. There's also no requirements to identity so it's up to implementations and currently that leads to many duplicate accounts.

Whereas, at a high level Nostr is a client and relay system. Your identity is constructed by public/private cryptographic keys (instead of as fractured identities registered on various different servers).

This is similar to email cryptographic signatures and also most blockchain implementations. Then content/posts are sent out to any number of message relays. Consumers of the content/posts do a map-reduce query against multiple relays to find content.

The benefits here is that if the relays go down, your identity is still safe as it's manifested by your keys. This also means that there's slightly less incentive for big centralized server dominance. Another benefit is that you don't need bidirectional communication across all (most) relays thus reducing traffic and storage costs as the system scales.

With all that said. I have no idea what Nostr looks like in practice or what the community health looks like. Or what community moderation tools exist. But from a theoretical standpoint it's a much more scalable architecture.