m1sterc001guy on Nostr: We didn't touch on it much but I can comment on it here. I'm a fan of both Spark and ...

We didn't touch on it much but I can comment on it here. I'm a fan of both Spark and Ark, I think there's value in having many robust protocols on top of Bitcoin. They each have different tradeoffs. In my opinion one of the nice things about Fedimint is that the tradeoff is explicit: you need to trust a quorum of the guardians. Very easy for users to understand.

The tradeoff in Spark and Ark is a little less explicit for the user. In Spark, it is self-custody unless the operator colludes with a previous coin holder. Ark has final settlement but only if your transaction participates in a round. Since the rounds are somewhat long, in practice I think most payments will be out-of-round payments, which have a similar trust model to offline ecash spending (you are trusting the sender to not double spend you). Ark also has a liveness requirement for end users (which comes with a fee burden to refresh your vtxo), whereas in Fedimint the liveness requirement is on the guardians and fees are only required when transacting.

I'll also mention that Fedimint is less "centralized" in the sense that it is a goal to not just have one federation, but many federations. Spark and Ark both rely on a central operator, which is convenient for most use cases since as I mentioned in the show, it is easier for bigger companies to operator quality services with high availability. But users can't switch between operators (to my knowledge) and if they go down the whole system is likely just unavailable.

I think privacy has gotten better recently in Spark but originally it was pretty bad. Fedimint and ecash in general is obviously built with privacy as a core feature (but at the expense of the custody tradeoff). If I recall correctly as well, Spark hasn't implemented the blind signing that Mercury layer (original statechain implementation) had, which is confusing to me. Maybe that's being worked on.

But as I said at the beginning, the more solutions the better. Users should use what works best for them! I've said in a different post that I think a statechain implementation on top of Fedimint would be really cool. Fedimint is modular, so applications other than ecash can be built. If that module existed, it would be as easy to run a statechain operator as it is running and ecash mint today. Users could opt-in to using either ecash or the statechain, whatever they prefer. And the trust model would be slightly better since it would be federated. Someone should build it!