If moving your neck and aligning your windows were major impediments to you, then you probably are better off with one monitor. But I think you are in the minority that doesn’t find at least a dual monitor setup beneficial.

I don’t have a Vision Pro, so I can only imagine how much nicer a virtual 27” 4K monitor would be compared to my tiny laptop monitor. I think the benefit should be obvious to anybody with an open mind about the idea, though.