Have you ever been inside of an industrial chicken house? Its absolutely, without a doubt, the most disgusting and depressing place I've ever personally seen. Even worse if you're unlucky enough to be there after a single case of avian flu is found anywhere in the area.

Chickens can be messy, but that's only an issue with free ranged birds if you don't have enough space for them. Most chickens won't venture too dar from their coop, usually on the order of a couple hundred feet. If you don't want chickens pooping all over your lawn and barn, just put their coop further out in the field (preferably near some trees for cover).

Rotational grazing is also really effective with chickens. Its more work, but you keep the birds where you want them and end up fertilizing your fields as you move them around.