I believe that the main difference between jumpers lie in the contact resistance. I use Nordost teminals
http://wheelstips.com/best-car-audio-battery-terminals with banana in one end and spades in the other. My speaker cables are spade terminated. That way, I avoid spade-to-spade connection which is difficult to "get rigth".
Before testing new cables/jumoers, it is very important to cut back some of the old acbles and make a "fresh" connection. Otherwise the new vs. old connection will drown out any cable difference.
And regarding cables, ALWAYS!!!! make the basic calculations of resistance, impedance and capacitance first, model them with the highly reactive load of our speakers and make sure that the cable is electrically suitable and doesn’t act like a filter. Even very expensive cables can do that, and then our brain can be fooled into believing that rolled-down treble equals more relaxed