It depends on too many things.
For horses to live out 24/7 they need a good amount of acreage or the pasture soon turns sour from all the poo and pee on it - but for many horses that amount of free grazing is a fast track to laminitis.
You also need access to shelter that they'll feel safe to use - a lot of horses are afraid to go in a confined space with other horses so they get to stand out in the weather and the biting bugs while their buddies enjoy the respite from it
And if a horse was born and raised to be stabled it doesn't see the great outdoors as a desirable place to be 24/7 any more than we'd want to go back to living in caves with no heating or electricity
I've recently bought 2 horses that became hysterical if they were expected to stop out too long or to tolerate bugs so its a new learning curve for them. When its snowy in the winter they spend most of their time waiting to be let into the barn because they know they have a choice.
Most stables horses can see other horses and even though my lot are outside with each other they show no interest at all in playing and rarely get close to each other - in fact anything that dares to touch Looby is treated with a loud squeal of protest and a sharp pair of hooves