Think of chin-ups versus pull-ups as underhand grip (chin-ups) versus overhand grip (pull-ups). While every lifter is bound to have a lot of feelings about the pros and cons of each, the mechanics come down to this: pull-ups are performed with an overhand grip and place more emphasis on the lats, while chin-ups place more emphasis on the biceps and pectoralis major with their underhand (or sometimes neutral) grip. However, this does not mean that chin-ups don’t engage the lats as the primary mover (they do) or that the pull-up doesn’t seriously recruit the biceps (it does).