Remember that "cooling" is limited to how much moisture the air can absorb. You can be bareheaded but if you are sweating more than the air can absorb then you'll have sweat running down your head. It's physics and no helmet will alter the air's ability to absorb moisture.
I have the Gage, the Volt, S-Works, the one below the S-Works, used the Atmos, and all of them had sweat dripping down my face while racing (22-27 mph avg) or on training rides (15-18 mph avg).
Any of the models above seemed reasonable in terms of ventilation. I had some helmets before (no longer made/sold) that were terrible, they really did limit air flow so much that it felt like I had a blanket on my head.
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"...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson