We are developing a DiffTool for comparing Microflow, Form ... for Mendix, I hope we will have the 1st release soon.
So it will look like this:
https://www.dropbox.com/s/5s7ofchpcxjrtab/eyecatching.png?dl=0
We recently had the situation where we wanted to revert some (not all) of the changes made in a revision that was a handful of revisions before the last one, while keeping all changes that occurred in later revisions. We thought we needed a way to compare the revision in question with the one that occured right after it, so that we could generate a complete list of differences and select the ones we wanted to remove. But as it turned out, a colleague knew that because the changes were restricted to a limited set of pages and microflows, the task could also be performed by only taking those from the revision prior to the changes, and putting them into the last and current revision. It's not an answer to your questiion, but it's a workaround in case reverting selected changes is the task at hand.