Ability to rebroadcast notes to other relays. No other service offers something like that yet.
Discussion
This would make user data more robust across nodes without users needing to nuke their battery life on a phone to publish to 25 relays, which I see as a common complaint. nostr.wine is the only group I see attempting rebroadcasting for users at scale, but it’s an even better fit for a backup node that might not need to be performant for most usecases