iTerm2: What is the best way to compare / diff two panes (like vimdiff)?

Question

I would like to compare two panes in iTerm2, like I can do it in vimdiff. (Or is it the best way to do it in vimdiff, not using iTerm2 panes??)

– I couldn't find anything in the documentation.

– And how can I search the iTerm documentation – – only with help of Google?