In Rio are they more likely to snatch your purse or to shoot you in a drive by?
In Rio they are more likely to kidnap you for ransom just for not looking like a bum. and failing that, they will just kill you outright.
There is also a huge problem with street kids turned pickpockets and worse...
I am sad to report the barbarism on the streets of Chicago, Newark, Somalia, Congo, Iraq, Afghanistan and other 3rd world cesspools is a demonstration of the NATURAL order of man. Left without the trappings of civilization all mankind will quickly resort to the same level of violence. Why these same violent acts are not prevalent in all places is that other people have learned to submit their natural impulses for the benefit of the community.
Chicago is the victim of decades of lawlessness, the breakdown of family, religion, personal responsibility and the dominance of a faceless and anonymous government. There are no boundaries or personal restraints and very little consequences for violent behavior.
What we are seeing in Chicago is the result of the government, both parties I might add. We have rewarded people for their lack of responsibility and turned our schools into a babysitting service. This problem can not be fixed in any short term period. Forty years of social engineering... See what we have created.
If Chicago is like L.A., then there are places to stay away from and you will be fine. Rio, however, could get you kidnapped and killed from even the good areas.