Edited entire question for clarity.
Scenario: Have 2 identical SQL Servers on separate servers, processing transactions from different applications simultaneously while being completely synchronized (example mobile apps server 1 and web apps server 2).
We are going to use Always On to fail over one server to the other for maintenance and vice versa however, when maintenance is complete, both servers will be once again online processing transactions from our various applications and synchronized.
Trying to solve a request from a client to be online, even during maintenance, with 2 synchronized servers, each processing transactions from different applications.
What is the best approach to keep them synchronized? Was leaning towards merge replication.
Current ver. SQL Server 2012 SP3-CU4
Thanks