I was in both cities this summer. Bluntly, here's my take:
Points for Chicago: Millennium Park beats Trinity Bellwoods, Mag Mile beats Dundas Square, Chicago River beats no river, waterfront is way better, overall - skyscrapers are more interesting and diverse (though that may change as Toronto incorporate and create new styles), better traffic management
Points for Toronto: No km wide ring of crap low-density industrial land surrounding the core in every direction like Chicago, way better mixed-income neighbourhoods (Wicker Park was the closest thing I saw to a hip urban neighbourhood in Chicago; Toronto has many areas at least as interesting), slower cars (better for pedestrian/patio environments), better international cuisine, greenery and architecture at UofT, Chicago has nothing quite like Yorkville and nothing quite like Kensington Market
Both are amazing, fairly-clean, big important cities with (nearly) world-class museums, vital economies and culture. In both, transit is great for some routes and awful for others. In both, there is limited greenspace throughout the city. They face many of the same challenges. Overall, Chicago probably has higher highs and lower lows; Toronto is more inclusive and diverse, and that is reflected in its land use. One of my favourite things about Chicago was the revitalized river, water front, and Millennium Park - all things that Toronto would be wise to emulate before these areas are covered in condos. If Toronto improves its public infrastructure and keeps up its pace of growth, by 2030 nobody will be making this comparison.