Why take the exams before graduation?
Because you know the fundamental subjects now, if you study 8 hours on your own using the FE or FS Review Manual and do your best during the exam, your chances of passing now are far above 90%. The pass rate for those who wait, is about 70% in the first year after graduation and dropping off fast for each year you wait (about 10% per year).
Another reason to take the exam while you are a senior is the simple application process. Just fill out a small form, mail it to ELSES, register online to take the exam and pay the fee. If you wait, you will have to fill out a longer application form, get reference letters, a transcript, a photo, notarization, etc.
So to avoid future headaches, do it now!