I believe a lot of the "differences" in titles depends on the company.  The company I currently work for has an Executive Asst but it has absolutely Nothing to do with secretarial work.  There is no Admin Asst since Admin is a whole department in and of itself.  There is Executive Secretary, Secretary II and Secretary I.  At a former position, I was a Personal Assistant (oh, how I miss that job), where I handled everything from letters, filing, office decor, shipping artwork, shipments to and from the tailor, paying bills and handling household payroll.