Indoor cats are generally healthier, if you give them enough enrichment. I live in a tiny little house but my cat has boxes to hide in, toys to play with, multiple spots to look out windows, etc. She won’t get sick or injured as much as an indoor/outdoor cat and will probably live longer.

Where I live you’re not supposed to let the cats roam free because it’s dangerous to them and they can get ran over, get diseases, hurt themselves without you being able to do anything etc.

I guess the local ecosystem is a plus but it’s mostly for the cat’s benefit afaik.