Electricity marketplace is a good example and is commonly mentioned as a killer-app for blockchain technologies. But what technology would you use to implement this marketplace?

Would you use a public, permissionless blockchain like Ethereum or should we use a private blockchain? There are private blockchains like JP Morgan Quorum (https://github.com/jpmorganchase/quorum) that is based on Ethereum software and allows to have >10K transactions per second. These private blockchains use different consensus methods that are much less decentralized than public Ethereum, all participants are known, and access to the network is restricted.

Would a private blockchain be a better fit in this case? If you would a public blockchain, could you elaborate why?