Peer-to-peer web hosting does not differentiate between clients and servers, all nodes can request and respond to services.
All Nodes can store data, they can both create and consume resources, meaning that a hosting's capacity to share resources will increase alongside the number of nodes present.
This method can be risky due the lack of security, many files found and shared on peer-to-peer sites can be illegal or dangerous to your operating machine.
Client-server web hosting does differentiate between clients and servers, a central server is used to store data and respond to the services requested by a client.
Client-server networks are more stable though they do start to fall off as client numbers increase.