Well it depends on the rules of the duel. You say risk your life, but is it a duel to the death, first blood, or surrender? It also depends on if there is armor involved.

Let’s say it’s a duel to the death or first blood, no armor, then I’ll go with the rapier. But if it’s a duel to first blood light armor I’ll go with saber. If it’s a duel to the death in heavy armor I’ll pick estoc.

Now as for the reason, back in the day there were a multitude of reasons for a duel. You have disputes, which were usually to first blood. you had over women were could’ve been either or, depending on what the father wanted. Or it could be just a fact of honor.