You're going to get a lot of different answers on this one. If you choose to use a wire bottom cage, make sure that they have a dirt bath and places to get off of the wire so they can rest their feet.
Personally, I like open bottom pens so they can live on the ground. For their happiness, they should have a minimum of 1 square foot per bird, and remember to subtract space taken up by feeders, waterers, and dust baths from your calculations.