I had received offer from both of these two universities, but I’m not sure which one is better in its undergraduate teaching. I found it hard to compare this two universities since they are so different in many ways. Can anyone help me with some advices about the pros and cons of attending either of them? 
Forgot to mention, I was admitted in CS major
The schools are so incredibly different that I think one will be a much better fit than the other in ways besides CS teaching. That said, I think RHIT would have the edge given its undergraduate focus. Again, it could be worse option for you personally still, or it could be the best option even if it was the lesser in terms of CS teaching quality.
RHIT = + undergraduate focus; - isolation
UMD = + variety of majors and people, national strength for CS; - large campus &classes