I want to add multiplayer matches to a game I'm making for Android/PC, and something echoed in my mind: would the network functionalities Unity provides work in Android? I ask this because Google has a free plug-in for their services, but Unity also offers possibilities. Also, using any of the above, do I need to pay to rent a server? Or, for example, since we need a paid developer account to register our game at Google Play Store, the servers are part of the deal?
Unity and Google offer different APIs/Services, but both are centred around a P2P (Peer to Peer) architecture.
Unity, as does Google, offers matchmaking and relay servers. These are ways to find players, and relay data between clients.
Unity's offering comes with a free "personal" licence, where as with Google's there seems to be some lack of information (free?).
As Unity is cross platform, it's tools and services are as well. The services provided by Google however only work on Android/iOS.
More information for Unity is here: https://unity3d.com/services/multiplayer
More information for Google is here: https://developers.google.com/games/services/common/concepts/realtimeMultiplayer