My oldest daughter is currently studying ChemE at IIT. Third year pretty far along with her BS in Chem ME and just started her Masters in Pharmaceutical Engineering.
The ChemE department is one of the smaller engineering departments so she has had great access to her professors and has never had a class with more than 30 students.
She and her friends have had good luck finding internships and/or on-campus research jobs. As far as recent graduate outcome from her ChemE, BiochemE, etc. friends, it does appear that they are successful in their goals (job, graduate school, MCAT/medical school, etc.).
Note that my daughter knew early on in her search that she wanted to go to small, private, STEM-focused schools (she chose IIT over Rose-Hulman, RPI, WPI, and Kettering.) So, I really do not have a good direct/personal comparison between IIT and UIC.
Also, note that I am an IIT alum and own my own engineering firm. I have not hired recently but IIT (along with Purdue and Iowa State) have been my go-tos for hiring CEs, ChemEs, and MEs. I have not encountered many UIC grads.
As one poster mentioned, engineering study starts our hard and only gets tougher and every school appears to have a rumored weed out class whether it is Calc 2, Gen. Chem, Organic Chemistry, etc. I do not think that there is a true weed out objective but those “weed out” classes are typically integral to understanding the theory and application of more upper level engineering coursework so they are going to be intense to help build that foundation.
As far as thing to research, look at who is hiring from both universities and what their industries are. For example, if he think that he wants to go into Pharmaceutical Engineering but most of the hiring companies from one of the universities are from oil & gas then dig more into the school that supports the industry that he wants.
Good luck to your son with his choice.