While it all makes sense in theory I think the scratch on the rear is better and have shot lenses with such scratches with seemingly no issues. The front scratches make the lens more prone to flare in my experience.
my brother once had a nikon lens that was not just scratched on the rear element, it was abraded in a huge chunk of the center of the element, but he still said it was one of the sharpest lenses he had and used it for commercial work.
we tend to think something on the lens will block light going to part of the film, but I suspect it does not work that way. I would suspect, but have no proof, that a front element scratch would cause more flare if in direct bright light.