A twin WDM-2/twin WDM-3A is more powerful, heavier than a small little Diesel Electric Locomotive aka EMD.
EMD is just meant for fuel saving, bit acceleration and nothing else inside it.
a Single WDM-2 can easily haul 15-18 coach train at a good mps.
a single WDM-3D/WDG-3A can haul 22-24 coach at a good mps.
a...
more... WDP-4/WDP-4B, does the same work, with extra specifications.
Now to sound more reality, a WDP-4/WDG-4 can't do the work of a heavy built X-4014.