<p>Look at the research programs of the faculty in these various departments. If there aren’t several people who you could envision spending several years doing a project with, then it’s probably not a good program for you. You should seek advice from your math and applied math professors about your interests and career plans, and which programs may suit your interests best, as well as asking them about the job market for math or applied math PhDs at Universities. University positions can be extremely competitive to get. So you should also investigate what alternative careers particular degree specializations may qualify you for in the event that you aren’t able to get a University position.</p>