I wouldn’t worry too much about which one is “better”, there are tons of companies hiring interns out of GMU so you won’t hurt for opportunities.
They are different experiences though. Have you visited both campuses? Did you get a feel for them?
Will you have to take out loans to attend UMD? If so, financially you will be behind the eight ball if you need to take out loans, and UMD will not significantly raise your starting salary.
So, if you’re going pure financial outcomes, GMU is probably a better choice, but the real answer is go where you think you will be most successful as long as it is affordable.