Different of the booster with power unit cylinder
(1)The booster is a device for high-pressure output, but they must to be 
    connecting with the others actuator and device to do work. Power unit
    cylinder is a high-pressure unit and does working itself.
(2)The booster must to be connecting with high-pressure tube and
    actuator from outside, so maybe cause some loss. Not at all loose for            power unit cylinder.
(3)The power unit cylinder is faster compare with booster.