I've read that the black one cracks easily, but that's just from one person's experience. DO you know if you can paint over that stuff? I'm not familiar. I just don't want a black floor. Lol
I will definitely look into ventilation. I was talking to my parents about what you told me and they looked at me like I had 3 heads lol like why so much for chickens. I am definitely going to do it though! Even for me it is way too warm in there and I keep the chicken doors open. I can't imagine what it would be like for the poor animals.
I've only had my new coop for a few months so I can't tell you, "Oh the black stuff won't crack," you'll have to ask me in a few years.

As far as ventilation yes, I figure if it feels stuffy to me inside a coop, how much stuffier must it be for a chicken who has to spend the whole night locked in there? Just for guidelines the recommended minimum is 1 sq ft per chicken or 10% of total floor space, whichever is greater. For me that would mean 12 sq ft minimum (that's what I built for) - so I put in over 30 sq ft of open windows and vents not including either the human or chicken doors.