Compared to the others, Nostr is optimized for innovation - it is easy to build new features on top and we'll see a lot of growth and evolution because of that. I really like that about it.
The problems I see with it right now are 1. Timestamps are easily forgeable 2. Difficult to control spam 3. Little incentive to run relays 4. Difficult to search the whole network
There are ideas on how to solve all of the problems, like POW on messages, like super relays(basically a mempool), there's a NIP for timestamps.
My guess is that it will evolve towards something that looks a lot like a blockchain. Decentralized Social is one of the few places where a blockchain actually makes sense. This will be interesting because the founding group is ideologically opposed to using a blockchain for anything but the holy BTC.