You can now get the Freight Train Starter Kit (with either engine) with an Auber RDK-300B PID controller instead of the standard Old Head PID.
The Auber is a popular option because of its large display and its dial for more convenient temperature adjustment. Instructions aren't shipped with the Auber, but can be found here: https://www.auberins.com/images/Manual/RDK-300B.pdf
The one disadvantage that should be noted is that the Auber uses a momentary switch to power on - meaning that it will not be able to be turned on (to heat up) remotely by a 'smart plug'.
So if being able to check the power status and power on/off your Freight Train remotely is more important to you, it may be worth it to save your money and go with one of the standard Starter Kits. If, however, that's not as important to you as being able to more conveniently change your set temperature, then the Auber is going to be worth the extra cost.
These starter kits come with everything that the standard ones come with, except of course the of the Old Head PID controller and its case.