That is a good question. As far as I can tell the only real difference are the people in charge of the organization. When Mas Oyama died there were three people who claimed to be the "True" successor of Sosai. Of course nobody knows who really is, and so they split into the three IKO's. Not to mention all the other little associations besides those. I would'nt think there would be a big difference in how things are run. Probably mostly just little minor details, although I haven't trained with these branches personally, I am part of the IFK (Internation Federation of Karate) headed by Hanshi Steve Arneil. I know that all the kata are the same and all.If you really want to learn about Kyokushin history I'd go to http://www.australiankyokushin.com. The site is currently under construction, but it's really great so look for it in the future. If you want to know more just ask. Osu! Sempai Murphy