Just to clarify my above post. Ultegra and DA are made from two clams shells that are glued/bonded together. Those are the ones that break from fatigue. 105 also has hollow arms and spindle, but is not bonded. Its made with hollow forged arms, that are a bit heavier but, to my knowledge, wont break. That would be my pick. Tiagra is made with solid arms and a hollow spindle. It wont break but is heavy, but fairly relatively inepensive.
EDIT: Its all in here.