I am doing the EMT class right now, so that i can work two long weekend shifs once I start clinicals next semster-thereby getting my hours in over the least amount of days. I was going to do CNA, but the class conflicted with my schedule. EmT takes longer, but they love part time people, and have 8, 10, 12, 16 and 24 hour shifts.
Also, I am working as a pharmacy tech while I take the EMT class, and my nursing classes. Tech-ing is a little less flexible, because there aren't any over night hours really. This summer, though, I plan to work at both jobs, as many hours as possible.
I say figure out your schedule, and then choose the one that fits best.
I will mention, however, a friend of mine said it is easier to get a hospital job with a CNA license than an EMT license. Depending on where you work as an EMT, you may or may not have alot of patient contact, as you mostly just transport people, whereas you usually will deliver more day to day care as a CNA (get to practice basic skills daily). Hope this helps.