NYC finished the year with around 330 murders. Still great for the size but not quite '200 at most'. I would say a driving factor is gentrification. In New York, it's rapid citywide and even beginning to reach the Bronx.

In Chicago, outside of a few neighborhoods it's not happening at all. There are still huge stretches of neighborhoods in the West and South sides with very little economic development, full of abandoned buildings. Just like in NYC back in the day, it's an environment that breeds social ills. Little economy outside the illegal, subpar schools, etc.

Of course I'm not trying to say that that's the only factor, just a significant one.