What exactly do you mean by "get uprooted"? As in having to move to another campus after the first/second year? Because you should also be aware that if you stay in Philly you might be moving around quite a bit for your rotations (I'm not 100% sure this would be the case, but the Danville campus's site highlighted that their students do their rotations all in one place/system, which was one of the selling points that led me to choose that one). But if you're adamant about Philly and you're interested in the research facilities, then I think it would be good to talk about those. If you want, mention one or two other aspects of why you like the Philly campus specifically, maybe you really like urban medicine or want to stay involved in a certain EC pursuit there. Just trying to throw ideas out.