a world of difference. i would invest the extra year and the the Master's. Do a job search- many epidemiology jobs require a master's and make no mention of a cert. if you want to work as an epidemiologist, you need the master's. if you have any rationalization for preferring the cert, this may change my response, but in the absence of this i would recommend a master's over a cert. 10 times out of 10. and i think their program is pretty good- i believe it is research intensive so you get to the know the faculty well.
