Portfolio depth matters more than gear
Most Chicago production companies have similar gear (Sony FX6, Canon C70, lots of LEDs). What separates good from average is whether they've done work in your industry. A film that nailed a manufacturing capability story is a stronger signal than a flashy commercial reel for a different category. Ask specifically: "Do you have work in our industry, and can I talk to those clients?"
Look for a documented pre-production process
Ask how they handle pre-production. If the answer is "we'll send a creative brief" or "we'll get on a kickoff call," that's a red flag. The good companies have a documented process: discovery interviews, narrative development, location scouts, interview subject coaching, shoot plan. Ask to see the process artifacts from a recent project.
Repeat-client references are the best signal
Ask for references from clients who hired the company more than once. One-time projects can succeed by luck. Repeat work is the cleanest signal of operational reliability. If the company can only point to one-and-done clients, you're rolling the dice on whether their process actually works.
Watch out for the gear-first pitch
Companies that lead with "we shoot on the Alexa Mini, we have a 5-axis gimbal, our color grading is on a DaVinci Resolve workstation" are pitching production capacity, not creative thinking. Both matter, but if the first half of the call is gear specs, the second half rarely makes up for it. The best companies talk about your story before they talk about their cameras.
The Chicago-specific question
Some Chicago production companies are specialists in commercial-broadcast work, others in documentary, others in event coverage. They're not interchangeable. A great commercial-broadcast company often makes a poor brand film, and vice versa. Match the type of company to the type of work you actually need.