Any of the files in Google Docs format (docs, spreadsheets, presentations, etc) already support versioning and history. I don't know how that effects the total storage however.
The interface seems different, the dropbox versioning appears to part of its file system, the google versioning as part of the application.
So for me, dropbox versions some blobs (truecrypt volumes) that it's not clear that google could version, unless they add a different interface to google drive (and I sure hope they do.)