What advantage does a Client-to-Client VPN have over other types of VPNs?

In a client-to-client VPN, the encryption and decryption occur at the originating and terminating clients respectively, so the payload remains encrypted across every intermediate network hop. Unlike gateway-to-gateway or remote-access VPNs where traffic may be decrypted at the edge before traversing the internal LAN, client-to-client VPNs maintain confidentiality for the entire path. This end-to-end model eliminates any cleartext exposure on any segment.

Client-to-client VPNs require that both client applications actively perform cryptographic operations - this is the opposite of not needing cryptography support.

End-to-end encryption actually makes QoS more difficult because intermediate devices cannot inspect the encrypted payload to classify or prioritize traffic.

Having the VPN gateway at the edge of the corporate network describes a remote-access or site-to-site VPN architecture, not a client-to-client model.