If you pursue paramedic education, you will not "work your way up" to a job as an ED tech. A paramedic has many times the education that a simple CNA or EMT has. To be honest, that is rather insulting to paramedics to suggest that the end point of their education and career ladder is a tech. We are working hard to remove the word "technician" from our title entirely.
There are several ER's in the nation where you need to be at least a EMT-P to tech. Techs even at the EMT-B level have the chance to interact with many more patients than an EMT working in the field. Even the larger EMS systems wont give you the patient contacts you get in the hospital environment. Ideally having a chance to do both ER tech and some level of field provider would best prepare you for your climb up the ladder, one step at a time. I know former techs that have gone on to EMT-P,RN,PA or MD and looked back at the tech experience as a real plus when it came to putting in clinical time.