Seeing the cats added in real time is clearly the way to go for modern applications. Feathers lets you create them in a snap and with a fraction of the code, thanks to the underlying Socket.io, which in turn uses WebSockets.
WebSockets are really not that complex and what Feathers does in this case is just listen for messages in the channel and associate them with actions like adding something to the database.
The power of Feathers is visible when you can just swap database and WebSocket provider, or switch to REST, without even touching your Vue code.