We have earthen floors in our coops. I love that, as if there is any moisture, which there is not really a whole lot of, pretty dry conditions up here, it can be absorbed into the earth. Back on the coast we had cement floors on the floors. Horse box stalls that were converted to chickens. Now that was nasty to me. With the wet climate, the wet chickens and ducks, always very ichy to clean out and had to be cleaned frequently, like monthly. I only clean out the coops twice a year here, after winter and before fall and there is no mucky muck going on, just debris. Personally, I like earthen floors.
But on the negative side of that, if something wanted to dig into the coop, by going beneath the walls, something could get in. We are in the open valley, with massive fields of alfalfa on one side and barley on the other. The places where the coyotes and such live are a long ways away, probably too far for them to come to bother to try to dig below the walls to get in. Not to say that it might not happen, but pretty clear area with not too much vermin around I guess. Been here almost two years and haven't yet to have a mishap, not to say, again, that mishap might come...who knows. The horses are close to the chickens and we have dogs, hopefully nothing wicked will ever this way come.
We had plywood in one of our coops back in the old life. Didn't like it because it got quite slippery, even with shavings and sawdust, but that was coast life, moist, humid, rainforest climate. Might work up here.
I think there is a lot of safety from predation of digging critters with a wooden floor. If I lived in bushy area, I would have concrete or wood floors for sure. But for now, I have only the earth, and I actually really do like it. Good topic, by the way, have a wonderful day, CynthiaM.