Conventional power units have a single oil supply circuit common to all outlets; no matter how many pressure outlets there are, they will always act as one. The pressure will remain constant across all outlets, which means the flow rates may differ. If the load is heavier on one side, for example, cylinders with less load will advance more quickly than those that are more heavily loaded. Conventional units are also simpler, more compact, and less expensive than synchronous units, and they may be preferred where synchronized lifting and lowering is not a critical concern. 

Synchronous power units feature multiple independent oil circuits, and are designed to produce equal flow rates across all cylinders, even if they are unequally loaded. Equal flow rates are achieved using specially designed piston pumps, valves and control devices, and allow the user to raise or lower practically any load evenly without needing to account for load balance.