Both seminaries are "Dutch," (URC & HRC). Both have expanded on their origins, to include Presbyterians on their faculties.
Generalizations are BAD, bad bad bad. Up front admission. My own school (GPTS) and WSC have a million things in common, and yet minor differences are made out to be night-and-day.
OK, so here's the generalization, with an anachronism and category error thrown in: MARS is more "Old Side," PRTS is more "New Side" (to borrow from 18th century American Presbyterian divisions). PRTS is unabashedly "experimental," its one of their openly promoted distinctives. MARS will bill itself as Reformed by the book--believing and doing correctly, which is seen as more important than feeling "correctly."
NEITHER PLACE would like to leave the impression that one is not DOCTRINAL or the other uninterested in a FELT Christ. Generalizations quickly become stereotypes.
Now, I will tell you that in order to decide where to go, you need to visit both places, and try to discern where you feel most comfortable, which professors you like best, etc. And wherever you go, you should realize that your spiritual formation is 90% YOUR TASK, and not the facilitating faculty of some school. You will get what you get by what you pull out of the school, and by growing in grace in church and personal devotion; and not by regurgitating the bare minimum on exams from assigned readings and lectures.