Alright so I’m not an expert so I might not be explaining it correctly.
Federated Network: Multiple instances sharing content, such as Lemmy
Peer to Peer Network: There is no “instances”, just peers. Many peers sharing content. Every user is a peer. There is no server costs, because every device connected to the network is acting like a mini-server. It will cost your device some storage space and network bandwith depending on the how the software is designed.
Or do you think Centralized servers are still gonna dominate the future?
In my opinion federation is the better peer to peer / decentralized service. Power is not centralized, but everything can be run as efficiently as a centralized service.