You would have to know the strand count and AWG size of the wire to compare two pieces of cable. Welding cable is more flexible because the individual wires in the cable are smaller diameter and more of them than that cheezy cable you get at Autozone or other outlets.
Welding Cable Class K
Class K welding cable is more commonly used, has 30 awg strandings and is available with a red or black jacket.
Welding Cable Class M
Class M welding cable offers better flexibility due to thinner 34 awg stranding and a more durable orange jacket.