Running a mix has several advantages. The first is that you can adjust the travel on each motor very easily and that will allow you to get the motors running the same rpm at top end.

The other reason is when you get more twin time you can even very easily mix the throttles to the rudder and when you make rudder turns the engines will help you make the turn. It is nice for scale and real fun for aerobatic spins and snaps

The main thing is to fly happy