Masters in Biomedical Engineering -- Duke or Johns Hopkins?

I’m not really familiar with either program and can’t speak to specifics, so will just offer a couple general pointers:

Regardless of where you go, you should assume that the responsibility of finding a research advisor will be on you. In fact, at this point, you should already have contacted (or be in the process of contacting) potential advisors to figure out who might have space and/or funding and/or projects for you in their lab and might be willing to take you in.

What’s more important is finding an advisor whose research interests (as well as space, funding, and availability) align most well with yours.