Thank you for your analysis. The current research interest of the Upenn group is what I am interested in but I don't like the proposal the professor made for future researches. The group from UMCP covers a wide range of research topics and the advisor gives his students freedom to choose from the topic pool during their first two years. I am pretty sure I will find my real interest there. So, in terms of research interest itself, UMCP fits me better. And the possibility of changing research advisor in Upenn is slim Actually, I tend to choose UMCP right now. But....I just cannot give myself any assurance of this choice....