
Originally Posted by
BigGreen
Pullups: overhand grip
Chinups: underhand grip
Pullups (done with their traditionally somewhat-wide grip) target the upper lats with great intensity and the rear delts with a "not to be scoffed at" intensity in addition to hitting the midpoint of the back provided you pull sufficiently far up. Chinups incorporate much more of the forearms and biceps, to the point where several respectable bodybuilders and trainers (rightfully in my opinion) consider a chin-up a bicep exercise in many regards. In addition, with it's closer grip, it has a reputation of hitting the lats further down, nearer the insertion.
Personally, for me the difference is DRAMATIC. At a bodyweight of about 250 even, 7-9 legit pullups seems to be my current limit. At this same weight, however, chin-ups regularly exceed the 13-15 range and beyond.