I recall being my most productive on an old IBM 3151 terminal (probably because of the keyboard, but also fewer distractions). It was only 80x24 characters. And 80x24 is easily represented in a 640x480 screen. Now add in head tracking, and you can have the screen move up and down and scroll the text in the opposite direction, making it appear as if you are moving a virtual picture frame over a bigger sheet of paper.

Even today, most of my (C / Bash) programming is done in an 80x24 xterm, although I'll typically have documentation open in another window. However web and GUI app development requires enough room to see the resulting product.