Five hours later, I returned home to find both of the glasses mid-froze. The outer edges of the water was solid, with a soft, juicy center.

It looked like a tie so far.

I waited.

After 9 seconds, I noticed the hot dogs and pulled them out for dinner.

 Two and half hours later, I checked again. The glasses each had ice freezing in concentric spheres, but it was becoming impossible to tell how much liquid water was left inside either. The one on the left, the cold water, looked frozen solid.

The ice cracked and popped as I coaxed it from the glasses.

I broke open both ice cylinders, and found my answer.

The cold water had frozen solid, but the hot water had only a little bubble of liquid water inside. It was about the size of a robin's egg.

The little ice-void is illustrated here with the help of a green peanut M&M.

The cold water wins! The dissolved gasses hadn't made a big difference, and neither had the hot-water evaporation loss.

I estimate that the boiled water would have frozen solid in another 40 minutes.

Thank you!