These are both very good schools. The main reason that I can think of for transferring is either if you want to be closer to home, or if there are financial benefits to attending university in-state. How much the financial benefit of being in-state matters to your family will depend upon your finances, which we don’t know anything about.
You can get a very good education at either school. You will need to keep a very high GPA at either school to have a good chance of getting into medical school, and a fairly high GPA to get into a good graduate school.
Since you are already at a very good university, I also would be reluctant to transfer to a community college in the hopes of getting into UMD in the future.
One thing that I wonder about is whether the fact that UMD just started having a neuroscience major would help you get in, on the basis that they might want to get some students into the program. I don’t see how you could find out other than by applying and see whether you get in.
It seems to me that there are three things that you can do: (i) Keep your grades up as much as you can at U.Mass. This will help regardless of what you do next; (ii) Try to continue to fit in at U.Mass, such as by participating in club activities; (iii) Apply to UMD and see whether you get in.