These 2 schools are not vastly different in perception at the undergrad level, and so I would suggest leaning towards the cheaper one. Also I heard that JHU is difficult at the pre-med undergrad level with significant grade deflation, but that is just the perception versus Vanderbilt and I would check that out. Finally, as another poster said upthread, if you actually do end up in medical school, the name and reputation of that institution will far outweigh your undergrad college.