I once worked for a researcher who probably did a bunch of his programming in the 1970s or so, when I guess he developed his habits. He did not like to review code onscreen. All of the code I wrote for him he wanted printed out so that he could examine and mark it up and take notes with a highlighter and pens.
That would suck when comparing between windows.
Or you could just use meld and a single screen makes it trivial to compare and apply differences
Or take screenshots and print them off and compare the two sheets of paper using a highlighter to mark them up. Easy!
I once worked for a researcher who probably did a bunch of his programming in the 1970s or so, when I guess he developed his habits. He did not like to review code onscreen. All of the code I wrote for him he wanted printed out so that he could examine and mark it up and take notes with a highlighter and pens.
I guess the workflow worked for him.