Personally I keep my horses out 24/7 unless they need to be brought in for a specific reason. I think they're happier, they get more excerise and in the wild, horses aren't in a stall. Also horses are herd animals and they're not in a herd if they're in a stall all day or most of the day. At least have your horse out during the day and inside at night.
I think a horse should have turn out every day. It's good for them and being stuck in a stall can cause them to be anxious. Though I also think they should always have shelter.
My horse has lived on pasture 24/7 since mid 2006 and he's always been healthy, sound, and happy.
Turn out is definitely better for the horse, as it allows him a more natural life, which is better for his body and mind.
When you keep your horse in a stall it causes so many medical conditions like arthritis and is really bad for their digestive tract because horses are supposed to eat a little bit all the time and in a stall they eat lots of hay at once if you don't put it in a slow feed hay net. It's proven that horses that are kept in a pasture don't buck,bolt or spook as often. Horses are supposed to be with their friends because they are herd animals and in a stall they don't get the proper exposure to other horses as they should.
I keep my horse in a stall at night because it's dark and can't see where he's going, so he could accidentally step in a gofer hole. But I let him out during the day time 😄