Like Bob I use 2 23" monitors side x side. I don't think I would want one large one unless it were 4k and even then I would have reservations as a large one would be too close in my environment.
 
I only use the 2nd monitor in some apps but it sure is handy at those times. I use the main for track view and the 2nd for the console, browser, piano roll, etc. In Vegas, pretty much the same. The track view in one and full screen preview monitor in the other.

All of this display talk has me jonesing for a 43-46" 4K.  As many pixels as 4 of what I have 2 of now at about the same size.  Over/under TV/MD that stretch all the way across with no "seam" in the middle.  Also keep the ones I have now for VSTi and other applications.
 
All I have to do is figure out to place them all with my monitors (PS8s) still in reasonable positions.
 
Saw a 46" LG 4K today for $380 ...

I dock the console view and then toggle with the D key between track and console.  Single 24" monitor here...

There are people still on 1 monitor?? heheh

I am about to upgrade to 4.

1 - track view
2 - console view
3 - Facebook
4 - Youtube cat videos

Come to think of it...4 monitors may hamper productivity.  But 2 is a must.