The difference is brown sugar! Chocolate chip cookies usually have brown sugar, and so does the chipless version. On the other hand, sugar cookies usually use granulated white sugar. As a result, regular sugar cookies are a bit more crisp and a little less chewy. Additionally, the butter flavor stands out in regular sugar cookies (because they don't have brown sugar to mute it), so they often taste more buttery. Chocolate chip cookies (and chipless cookies) are chewier with flavor notes of molasses and buttered caramel.