Well I think in my case prior contact with faculty had a big importance, and the fact that they might have been familiar with some of the people who wrote my LORs. Also, it really helps to talk with current students who can shed light on the department and relevant faculty members you might have missed out (you're welcome to make contact with me next year). I think for every program - the more inside knowledge the better.
I will say though that as time goes by I am increasingly unsure of JSP's positioning for later placement - I think that for people with a law undergraduate degree/JD perhaps going to a disciplinary program might be even more advantageous.