I like vimdiff, since it's fair quick to collapse and expand code chunks if you know the keyboard shortcuts. Actually, since it's vim, knowing the keyboard shortcuts is the entire game lol.

I usually have vimdiff open in a horizontal pane in tmux, then use the other horizontal pane to look at other code that the change references. Could I optimize and have everything in a single vim session? Sure, but at that point, I'd also want cscope set up to find references within vim, and I'm now trivial steps away from a full IDE in vim.

.... which people do have, and more power to them. But alas, I don't have the luxury of fastidious optimization of my workflow to that degree.