Both excellent schools. You will not go wrong with either, but they will likely be very different experiences. Rural vs. Urban. Small vs. Large.
I am a firm believer in the LAC’s and that you only have one chance to have that sort of experience. You can always apply for graduate school to a larger university. At a school like Williams, undergraduates are the focus. You will be in a pool of 2k undergraduates, compared to Johns Hopkins 20k plus students. I have friends who have kids at similar schools and both have said the same things- equally outstanding educations, but at the smaller LACs, the opportunities find their way to the student and at the larger schools they have similar opportunities, but they have to work a bit to find them. The reality is, you will likely do well at both of these schools and come out with an outstanding education, but where will you feel like you got the most out of the experience? Only you can answer that. Best wishes to you!