There was a report done by a MC magazine in the states about helmet design and testing standards.
http://www.motorcyclistonline.com/gearbox/motorcycle_helmet_review/index.html long article.
It raised several very interesting questions regarding load transfer. It found that some of the cheapest helmets were actually better in reducing g loading than the more expensive ones. This was put down to the fact that the helmet flexed a little more allowing the eps liner to do its job more effectively.
It also raised the spectre of helmets being designed to pass the tests required by one standard and failing when another set of standards was used.
There was a follow up article to this, that I can not find, that showed in table form how the various helmets did.