Hedera is a permissioned network because they are operating at the theoretical frontier of speed and security. Eventually, this will be a permissionless network, but they will do so progressively without sacrificing security. The hashgraph algorithm is highly decentralized - there are no leaders, miners, coordinators, or block producers with special influence towards consensus.
The hashgraph algorithm is open review and all the services are open source. Anyone can propose changes thought the HIP program. Hedera has better throughout than [X coin] before sharding (250k-400k tps) and will experience less latency as the network expands (through a consensus mechanism that is at the theoretical limit of simplicity and efficiency).
Sources
Is the Hedera network decentralized?
Hedera.com
Thanks to https://twitter.com/ArragornV and https://twitter.com/NicholasVottero
