"Coolest" is seriously subjective.
As for the Chicago layout, I'm still ticked that the last time I was there in 2002, the entire lower floor was blocked for the layout construction. I missed my one chance to get a close up view of NYC 999 and I'm still ticked about that.
But as for "Coolest," I don't think Chicago (or any other American layout, to be fair) can hold a candle to the Miniatur Wunderland layout in Hamburg, which features an amazing amount of HO track, highways and roads with self-driving, computer-controlled vehicles, complete towns, a real water port with floating ships, and a full airport with planes which actually taxi out to runways and take off and land: