Adding to what Molarbear said:
SIU Pros:
-Cost of education
-Cost of living
-Didactic Education (#4 in the country in board scores, UIC scores are pretty average)
-Technology/Sim Lab (which UIC lacks)
-New Facilities (UIC's are pretty ancient)
-Focus on implants? (not sure if it's true, that's what I heard)
-Good patient base? (I assume there's no shortage of rednecks with methmouth

I kid, I kid.)
-Safe area (UIC campus isn't that safe at night. or during the day? my dad got his car broken into in broad daylight on the UIC campus with a cop car parked a block away)
-Proximity to University of Illinois campus! GO ILLINI!
😉
UIC Pros
-CHICAGO! Location, location, location. (SIU board scores are high for a reason, they have nothing else to do but study lol. I read in an old SDN post that going to SIU dental school in Alton was like being locked up in jail for 4 years, though that person ultimately found the experience rewarding...)
-Diversity (a priority here, you'd be hard pressed to find a more diverse dental school class)
-Clinical Education (there might have been a battle for patients when Northwestern and Loyola had dental schools, but now UIC is the only dental school in Chicago, which is really ridiculous. you won't find a better patient base anywhere else, and the clinical training is superb)
-Cheaper than a private school (like Tufts) lol
They are both great schools. Objectively, SIU is probably the better choice, all factors considered. And if you wanted to practice in or around Chicago, you could do that after you graduated. I didn't apply to SIU though, location and diversity were my main priorities, and UIC was near the top of my list of schools.