It really doesn't follow this pattern - a lot of Chicago students have no ties to the city, and a lot of UPR students have never left Chicago before (or at least spent the majority of their lives there); keep in mind also that the majority of true OOS students will want Chicago, so you'll have most OOS, Chicago, and suburban etc-wanting-to-get-into-the-city students all trying for that campus. Remember also that anyone in the Urban or Global Health track programs automatically gets Chicago, so if you're not in that - and the commitment is not worth it if you're not interested, please don't use it as a way to get Chicago - so that means even fewer spaces.
The best bet of getting Chicago honestly seems to be to interview early-mid cycle when there are still spaces open, or be waitlisted and taken off in the middle of the summer. But, it's still really not that predictable. And seriously, where you interview does NOT indicate where you'll be assigned. My significant other and I both interviewed in January of our cycles (he early Jan 2014, me late Jan 2015), he in Peoria and I in Chicago; he was accepted in late January and assigned to Chicago, I was accepted in March and assigned to Rockford. Yes, the school knew we were together and put us in separate campuses, but oh well - I spent the year on the East Coast so a couple hours' drive really isn't anything 😛 Both of us grew up our entire lives in the city of Chicago and have made every indication of practicing here when we're done with medical school. Interestingly, I got changed to OOS status this past year because my parents moved and I needed a permanent address while on the coast, so I became OOS and got UPR (same happened to a classmate of mine).
That being said, a lot of people on the UPR track really love it - Urbana is a really fun town with fantastic research opportunities, Rockford has a unique longitudinal program where you have your own patients already as an M2 (this is so beyond cool and I honestly don't think I could get a better clinical experience for what I want to do, so I'm elated to be at Rockford even if Chicago would have been "logistically easier"...the SO is a little mopey though 😛 ), and Peoria has a new simulation center and leads in neurology and other specialties. Peoria was personally my last choice, but the friends I have going to Peoria (also city people) seem to be very happy. Chicago is fun, but you'll have time to explore it even if you're at other campuses (a lot of UPR students do research in the city in M1 summer, and visit on the weekends etc) - you don't need to be there alllll the time because honestly it's better to be less distracted with medical school anyway. Most importantly, the people at every campus are exceptional because they all come through the same interview process and decision, so if you love the people at your interview and think that it's the environment that works best for you, give it a good look regardless of campus. That's why I chose UICOM. 🙂
Sorry for the long post, but the admissions process (especially for UICOM) can be confusing so I'd like to help where I can!