Best way to throw a round kick for MMA and instructions on how its done?

There are so many variations on this kick, so can you tell me the variation thats gonna be the most useful? / Is the most powerful/ Is the most...

Source: http://www.mmaforum.com/standup-technique/104679-best-way-throw-round-kick-mma-instructions-how-its-done.html

Marvin Eastman  Stav Crazy Bear Economou  Yves Edwards  Justin Eilers  Jon Olav Einemo