Winning an argument is usually what most people would prefer however, depending on your opponent and what tools they bring as their defense, should help decide whether one goes in for the first word or the last. Sometimes defeat in an argument is in the best interest if consequences with winning brings on an ill-favored event. Say for instance you find yourself in a disagreement over who just won a poker game and your opponent (you suspect) is packing a gun. Just swallow your pride and walk away with your life. Although the wounds of losing hurts the ego deeply, (and so you lose a few $$) some say this may be the real victory and you get to live a bit longer as well.
Whatever argument you may find yourself involved in, remember this anonymous quote:
It is far more impressive when others discover your good qualities without your help.
Refraining from speaking the last word in an argument could lead to true humility.