When I first started in my original city I put in a lot of POIs. As I expanded I stopped putting them in. However, missions seem to generate in all of my areas (16 counties in Florida) equally. And...in my original area, there does not seem to be missions generating in things like the high rises, parking garages, and others that I put in (but in the beginning I used to get a lot at the POIs.
With that being said, what are the advantages of putting POIs all over?