Screaming Frog SEO Spider could do that for you. You'd need to set up a custom filter to look for a copy identifier (ie: a div that always contains the main copy) and have it scrape that for you while it's crawling. Do the same for the other site and then you could match them up pretty easy I think.
Here is a good resource on different ways of using the tool - http://www.seerinteractive.com/blog/screaming-frog-guide We use it almost daily for a variety of tasks and find it to be pretty flexible. Good luck!
