The slide winch looks a little bit different in that it has a purpose-designed plate that slips into a rail already mounted on the side of the trailer. Upper and lower lips built into the rail hold the winch in place. By the way, there are both single and double sliders. The double slider utilizes a double rail with upper and lower sections.
The biggest advantage of this kind of system is flexibility. It can adjust to accommodate any load configuration. The downside is having to mount rails on the trailer. More can go wrong with this sort of system.