When uploading new versions of raster graphics, we get text like:
"Foo uploaded a new version of File:Bar.jpg:..."
followed by whatever text a user chooses to insert as an edit summary. In the case of two separate JPEGs, that's probably the best you can do, but with vector graphics we could actually display differences *in* the SVG itself. It seems like this could be a very doable and useful function for spotting what the actual differences are between revisions of an SVG file.