Well I'd honestly say GSP is more of a wrestler at this point who uses more of a boxing approach than a kyokushinkai approach for his striking these days. Machida uses Shotokan as his primary approach. Jon Jones uses boxing. Josh Barnett is a Catch Wrestler (yeah yeah I know submission wrestling is submission wrestling and more differences are individual style choices, there are some differences though from typical no-gi BJJ and he was trained by the likes of Billy Robinson, Antonio Inoki, Funaki, Erik Paulson and others who had Catch wreestling/Shooto roots). Fedor uses Sambo.
Member of DaJoGen MMA school under Dave Hagen and Team Chaos fight team under Denver Mangiyatan and Chris Toquero, ran out of Zanshin Martial Arts in Salem Oregon: http://www.zanshinarts.org/Home.aspx