Both places can be pretty rough, but Denver for sure.
Colorado Springs is a military town, and has a pretty high rate of petty crime, meth use and overall stupid shit happening.
Denver's got alot of crime in certain areas and tooooooons of homeless people, but its a pretty big city.
If you havent found a place yet, Avoid the east part of the city. Stay west of Colorado Boulevard.
I've lived all over the city. DM n I can give you way more in depth answers.