It’s the little things that make the difference; in this case they can be as small as the pins in a Deutsch plug.  A properly crimped connection is as good of a connection that can be made; a poorly done crimp can be the source of intermittent failures, increased resistance, even an ignition source and will ultimately fail. Those over at Diesel Magazine wrote an article in the September-October issue of diesel workshop which can be downloaded for free here that articulates how to inspect a freshly crimped connector to determine whether it is acceptable or not.