Stellar is pretty interesting to me1. It seems to scale better than just about any other cryptocurrency implementation I’ve seen. It also doesn’t seem to require either proof of work or proof of stake. I still don’t understand how it can avoid sybil attacks without at least one of those. That’s not to say that I don’t think it’s possible. Just that I don’t understand how it does it.
Lightning was originally proposed as a solution to Bitcoin’s scalability issues. Stellar would appear to not need that. At least: not yet. The fact that they’re pursuing it anyway is pretty interesting.