Elbow and wrist must work together in order to maximize the efficiency of the arms, you can extend elbow and contract wrists to force-straighten your arms(not a common case but sometimes you can cancel an elbow lock)and otherwise if you want to contract the elbow,if you ask which is better, none is, each option has its own pros and cons, i know it sounds overused but the best you can do is to adapt to the situation once again.