The main difference is spreading out the control of the database to multiple actors. No single entity is allowed to make unilateral changes to the state of the database.
Moreover, the line between permisisonless and permissioned blockchains isn't necessarily about who's allowed to join but rather which identity they use. For RRR, the only reason we limit ourselves to permissioned is because we require long lived identities to prevent sybil attacks; otherwise it's as "open" as any public blockchain.
Moreover, the line between permisisonless and permissioned blockchains isn't necessarily about who's allowed to join but rather which identity they use. For RRR, the only reason we limit ourselves to permissioned is because we require long lived identities to prevent sybil attacks; otherwise it's as "open" as any public blockchain.