The argument goes round in circles: an indoor cat is bored and unnatural, an outdoor cat is happy until the day it does not come home.
What outdoor actually means here: traffic, other cats and the fights and abscesses that follow, dogs, poison put out for rats, people who do not like cats, and the risk of it simply being taken.
What indoor actually means: a cat that needs you to provide everything it would otherwise find for itself -- climbing, hunting games, a window with something happening outside, and a second cat if it is the sort that wants one.
There is a middle path some people use: a netted balcony, a supervised roof, or letting them out only in daylight.
Which way did you go, what happened, and would you choose the same again? If you lost a cat outdoors, that is worth saying too -- it is the part nobody posts about.