Been developing software for 30+ years, with up to 2 extra monitors, and I always go back to a single display. I'll put myself up against anybody with multiple displays. The thing is, I just alt-tab (or otherwise) to different things - it's not like I can actually perceive more than 1 window at a time, for the most part. The head twisting to see multiple displays bugs me, as does the eye movements across a huge display. Plus there is just more opportunities for distractions with more display area.
Finally, I work most effectively when I hold what I need in my head, and find that multiple displays fights against that need.
The only real exception to that is if I'm writing front end code of some sort, having the live updates helps a ton.
Lastly, if I could have a bigger display on my laptop, I'd be up for that!