I am preparing for Trinity Firefighting Robot Contest America. and I need fast legged robot of the max size 30cm X 30cm X 30cm that use RX-24 servo from Robotis. The arena will be maze and perfectly flat. My robot upper body is perfectly symmetric so its lower body or leg doesn't need to rotate its face to another direction but still need turn its motion for maneuver inside the maze.
Hexapod robot with tripod gait cycle will be both more stable and faster in terms of the locomotion speed. It is more stable because the support polygon of the tripod gait is a triangle. But in return you have 6 more joints and hence 6 more servo motors, which increases the power consumption and the complexity of the system.