Docking Station for Latitude 5570

Is it a 5570 or an E5570?  The difference matters because the "E" prefix means that the system has a docking connector on its underside.  If you have that, then the correct docking station options are the E-Port with USB 3.0 here or E-Port Plus with USB 3.0 here.  The difference is that the regular version allows you to have a display connected via VGA and then you can also use either the DVI or DisplayPort connector.  You cannot use the DVI and DisplayPort connectors on the dock simultaneously, although the DisplayPort connector itself can drive multiple independent displays from that single connector if you have displays that support daisy-chaining or you use an external DisplayPort MST hub.

By comparison, the Plus version has two "banks" of DVI and DisplayPort connectors, and you can use one connector on each bank simultaneously -- so you can for example connect two displays via DVI or two displays via DisplayPort, or one display to each one.  It also supports daisy-chaining out of its DisplayPort connectors.  Lastly, the Plus version also has some legacy connectors if you have some ancient peripherals that need them (serial/COM, parallel/LPT, and PS/2).

Bottom line: If you want to run dual displays AND don't want to use VGA for one of them AND your displays don't support daisy-chaining AND you don't want to buy an MST hub, then the Plus version makes life easier.