Both are valuable in a different way. As an ER tech you will mostly be doing vitals, moving patients, etc depending on the facility. You will get a pretty good understanding of how an ED operates. The downside is that there is very little assessment that you will personally will be doing outside of setting the patient up on the monitor. As an EMT you do quite a bit more. For the duration of the transport you are the sole medical provider for the patient with all of the responsibilities that this requires. You get a very different perspective on medicine, learning about issues that affect your community in a much closer way then you would from the ER itself. That said, you have far less exposure to physicians and thus it’s harder to build connections for shadowing etc.