When I saw for the first time SN (early days) I said: this is it! This is the old Bitcointalk forum but with sats! Will make Satoshi proud about it. Even the name is SN like Satoshi Nakamoto initials! On SN we can have a lot of things that NOSTR can't do it. I see them complimentary not competing. Yes they can interact each others (we have now crossposting) but are not eliminating each others.
NOSTR is totally something else and many people see it only as a new twatter, but ignore the other parts: market, identities, relays, wss, p2p trades etc. I do not like how the zaps were implemented into NOSTR. They should use the standard LUDs that works perfexctly and much better than zaps. SN did wonderful job with implementing LUD-12 and LUD-18 for example. These are 2 LUDs that are really underestimated.