I"m not sure I understand your question; NATS streaming server (built on top of NATS) supports persistence to disk, a raft group, a SQL table, etc. and it appears the various storage implementations have mechanisms [0] to delete or compress old data.

That being said, I don't think this is what differentiates the two systems, the guarantees they do/don't make are likely what will make the decision for your project.

[0]: https://github.com/nats-io/nats-streaming-server/blob/master...