I'd be interested in the definitive answer, but the math appears to be over my head.
Some of it has already been done:
https://upload.wikimedia.org/wikipedia/commons/f/ff/Wind_chill.pngIf the air temperature is 35 F, driving at 30mph would be the equivalent of standing still when it's 22 F out, and driving at 60mph would be equivalent of standing still when it's 17 F out.
The other relevant information is Newton's law of cooling, which states that the "rate of heat loss of a body is directly proportional to the difference in the temperatures between the body and its surroundings provided the temperature difference is small and the nature of radiating surface remains same."
Piecing those together, I interpret it to mean it'll take the same amount of time to bring your body temperature down to 22 F at 30mph as it would to bring it down to 17 F at 60mph.... assuming that it stopped producing any heat I think.
But the 60mph trip would be cut short in half if that's the distance your determined to go. Assuming temperature drop is linear (probably not, but the math is too much for me to understand), going 60mph your body temperature would only drop to 57.8 F on the same trip that would drop your body temperature to 22 F going 30mph. Again, you're body isn't producing any heat in this scenario.
So obviously this should all be taken with a good helping of salt, but I think the increase in speed outweighs the increase in wind chill.