I had an Orbea Orca locked up with a fairly inexpensive and lightweight chain lock stolen a few years back. I was in an appt. for 90 mins. in a highly trafficked area at 11 in the morning. Thieves here will steal any bike at any time of day. They don't care. Fortunately, I am conservative and I had good insurance.
If you don't want your nice new bike stolen in the city of Chicago, I would highly recommend that you pick your lock based on what you feel is the best available, whatever the cost. You want to have a lock that causes thieves to just want to move on to something easier. It's well worth the investment.
I use a steel, 16 mm Sigtuna that is built like a tank. Extremely heavy. It could be a bit of a deterrent. And, as mentioned above, I bring my bike into my apartment with me. That's the best bike lock of all.