I have heard that wire is good, for the easy ability to clean. I just don't want to have buy new stuff, or build a false bottom i have to remove.
Also @ Michigan Transplant: I am no expert, merely a novice such as yourself, however; any time of year can work for your broody hens. People will advise you to move them, in the winter, but if u check the "incubating chicks" forum you will hear of people having broody hens hatching eggs in negative temperatures, and with at least a foot of snow on the ground. The chicks will always be able to find comfort and heat underneath the mom. I have a broody hen (a silkie bantam) on top of 10 full sized eggs and she seems to be fine. I have however, moved her inside to a quiet place with access to food and water, and even gave her a small red 75 watt heat lamp for a little added "comfort". I candled the eggs yesterday (day 11) and all seem to be active and growing!! Bantam hens can usually clutch up to 12 eggs and do just fine. I have heard people say however; that their full size hens have clutched, hatched, and raised more than 15 chicks.
I would say that broody hens normally raise and clutch babies in the spring/summertime. Their natural instincts will tell them that is the best time of year for the most successful hatch, however, as i said before, u can literally hatch eggs with a broody hen all year long. Get some eggs and start making some chicks!!! and then take some pics so we can all watch!!!