well the fixed one you would put a fixed sproket on if u had a freewheel on the front, but if you had a fixed sprocket on the front you would need a freewheel on the fixed hub. the "non fixed" you would need a fixed sprocket on front.
The new echo free hub is good though because it has 72 engagements, weather or not the hubs will last long well...... thats a different story.