I all depends on how you like to work. The snag with two monitors is that you’re always looking down the crack (so to speak 
) and if you move them so you have one primary monitor with the other one to the side, you have continually to turn your head, which is bad for your neck.
My solution is to have a 27" on the desk, and a 48" on the wall, both of which I can see without moving my head.
DG