You can get a lot of different opinions on this and that is what it is, opinion and personal preference. I personally like the coop itself to be a bit darker, I think mine are calmer when it’s not so bright. Others have really bright coops and like them. As with everything there is no real right or wrong answer. I do want enough light in there so I can see to work and the chickens can see to get around.
When a hen is looking for a nest she instinctively looks for a place that is a good hiding place. She is looking for a place that she thinks predators will not find her nest and eat the eggs, or her for that matter. Darker spots often appear beter hidden. That doesn’t mean some hens won’t choose a nest right out in the open, who knows what their bird brains are thinking, but when mine try to lay somewhere other than in a nest they normally pick a fairly dark secluded place.
I don’t know what your nests look like or whether you are counting on that window for ventilation. I don’t know where your roosts are which could influence where I’d put that window. Mine like to roost right next to my window and I open my window in the summer for ventilation. It’s closed right now.
If your nests are built with a top so they are dark inside, I don’t know that it makes that much difference. Not knowing anything about your ventilation or roosts, the north wall would be my preference if north and south are the only options. Even in Maryland heat in summer is probably more of a danger than cold in winter. On the north side the coop will stay cooler in summer.
I like the nests on the north wall for the same reason. Depending on how they are built, if they are on the south or west wall they just might become little ovens in the summer. That north wall will be cooler.
