Always On: replication over cross server SQL instances
Depending on your requirement, both solution are OK.
In first schema, imagine to have a fault on a server. Or you simply need to do updates. Can a single server handle your work load? If yes, you can save money.

You will need to handle correctly multiple IP for server, or different port for the istances, but it is not a problem if your department is skilled.

I mixed mutiple istances in multiple servers, also mixed failover cluster istances with Always ON. My only suggestion is to implement on SQL 2016 or 2017 if you can. It introduces DAG and is a bit more mature.