Haha, I've lived on campus all 4 years as well. I lived on campus as a freshman, lived on and worked the front desk as a sophomore, and I've had the joys of free housing and meal plan for the last two years as the Desk Manager of my building (on the RA staff). It will definitely be a culture shock, but I absolutely love my old roommate's current apartment that is about a 20 minute drive from campus and the fact that it's her "getaway" from being on campus all day.
I've considered living on campus especially since Northwestern has graduate-specific housing options, and it's still up there as an option. Not having to furnish an apartment or pay utilities would be a huge plus especially since I would be 6 hours from home. I would choose living on campus vs an apartment right off campus not affiliated with the university. Another great thing is that since you would have a kitchen in graduate housing (assuming), you wouldn't have to purchase a meal plan or maybe a smaller option that has limited meal swipes and the ease of budgeting your own money instead of paying a higher rate.
Definitely going to be a tough decision, but I keep leaning towards wanting to get a cat as my grad school companion, so that's the issue I'm having with on campus options.