My Houdans with V-combs and small wattles weathered our unusually cold (a week of temps in the teens) southeastern winter with flying colors. We had a learning curve with figuring out waterers that would stay ice-free long enough for them to drink without getting their crests wet, but even with some wet crests... didn't lose any points.
Leghorns did OK but I did lose some points. Legbars, surprisingly, suffered the worse. I can't figure why the difference. I dubbed several frostbitten Legbar combs, though, and realized they're much thicker at the base than the Leghorns. (Dubbing them was NOT fun.) I don't know if that is relevant or not.
We have severe hot and humid summers here as well, and I haven't noticed that big combs gave the leghorns and legbars any advantage over the Houdans. They all kept laying right through, no heat-related losses, no indicators of being stressed. I've heard a big comb would help with sort of evaporative cooling or something, but with adequate husbandry it seems like a non-issue.
