At the end of the day, the most important part of a PhD is the research. When you apply to jobs or faculty positions following your PhD, people will ask what research you did because that will ultimately determine your future. Although life outside of graduate school is important, the majority of your hours will be spent in lab.
Personally, I am choosing attending UCSD because I felt like the research interests of the faculty aligned well with my interests, I really connected with all of the people I met in the program, and I love San Diego. I don't know too much about JH, so it is hard for me to compare the two. Good luck deciding!