Depends on how bad you need the dough (always a concern for me. I can't really do a lot of pro bono things anymore, bc i'm so da#n poor.
I agree that you can get a lot out of a research project that'll distinguish you and allow you to bring more to the table in your app and interview, but working as a tech can provide that as well as long as you keep your eyes open (noticing trends in sales, treatment, workload. you gotta always be evaluating where you are and what you're doing.)