What time would they be turned out at? The horses at my barn are turned out at 8:00 and brought back in at 5:30 or 6:00, which is about ten hours of turn-out. I don't think that 10-12 hours in and out sounds that bad either, depending on what time they are turned out at. Just go with what you think is best. Do you really like the barn you are at right now? Does your horse like it? If you haven't taken a tour of the other barn, maybe do that and see if you think it's an environment that your horse would do well in. See if you like it, and if the people are friendly and helpful. Also, if it's $175 more than where you board right now, make sure you are certain that you can afford that.
I wouldn't start thinking about how the owners of the barn you are at would feel about you leaving- I know it's hard and I feel that way all the time about everything, but you are doing business together, don't let sentimental reasons stop you from moving to a barn that you think you and your horse would like better.