Performance difference between jumper cable and Lithium pack

Cable length, that's the long and the short of it. 12 volts isn't a lot of juice. It doesn't take much fall-off due to wire resistance to cause trouble. My jumpers are 20 feet long and double aught wire -- essential for cranking a diesel. My booster box, the leads are at most 12 inches. That makes much smaller wires very feasible. And they are.