How good are alligator clip connectors for electrical connections?

I am trying to extend the length of an electrical wire. A simple way to do that has been to use connector wires with alligator clips on both ends and use that to extend the connection. What I am interested is whether these alligator clip connectors will drop the current or the voltage? I've measured the resistance of the circuit with and without the alligator connectors, they are roughly the same. 2.060 M ohm vs 2.054 M ohm. Should I continue to use alligator clips or should I get new connector wires and solder them in for a better connection? Is there a significant difference between alligator clips and a soldered connection? The resistance doesn't seem to indicate much of a difference.