Does a short arm or long arm have advantage in arm wrestling?

A long arm of the same power would produce more leverage and torque, but I think it's more will power, and who has the most of that.

This is completely wrong. Think of the two arms acting as levers. Would you have an easier time pulling a short lever or a long lever?

Obviously the long lever is much easier to pull so the longer armed person would be at a disadvantage because his arm acts as a longer lever than the other persons arm.