6 digits are less secure than 100 characters because when asked to generate a 6 digit password, many many people will pick their birthdate, wedding anniversary,

6 digits are less secure than 100 characters because when asked to generate a 6 digit password, many many people will pick their birthdate, wedding anniversary, or childrens' birthdate. With an alphanumeric password, many people will still pick a variation of "password12345" or "letmein!!", but at least then their banking password is not literally posted on their public Facebook page. :)