Not letting unregistered users edit controversial pages at all is surely less intrusive than holding their edits for review?
Yes, because I think 99.9% of all unregistered user actions are reading, not editing. Therefore we are dabbling with the unregistered user's Wikipedia experience in a much larger way - not by holding their edits, but by not showing the most current version (which, by the way, will in most cases not even be an anonymous edit).
Ulrich