Hi, I'm also a recently certified EMT, and have been working for a private ambulance company for the last few months, part-time. Our company has 911 contracts with several towns, and we do a lot of routine transports as well. About 60% of the calls I do are routine transports, the other 40% emergency calls. EMT is not a bad way to get your feet wet in the healthcare field--you'll get to see some interesting pathology and clinical presentations, which will complement some of what you learn in your studies....Thefirst severely jaundiced patient I ever saw, for instance, was a motivator to do some further reading on the causes of jaundice, blood composition, and liver function.
If you work for a company that takes 911 calls, you will get a lot of experience doing patient assessments, taking medical histories, taking vitals, forming a clinical field impression, and just dealing with a wide variety of people, some very nice folks who appreciate your help, and some who constitute the dregs of society (I know, not p.c. to say that, but true nonetheless). In short, the EMT-B ticket opens the door for you to work as an EMT-B, which will gain you some interesting experiences, and which is where your education as an EMT really begins. If you already have your cert., it would be invaluable to work in the field, even if only for a brief time, just to see what it's all about.
I can't speak for the CNA job, although I'm sure you'd gain a lot of knowledge and experience doing that as well, and the experience would be hospital-related and may give you better insights into the health-care field in general than working in pre-hospital care as an EMT.
Good luck