If I were to pour really hot boiling water onto a bowl, which would have better heat tolerance, the clay or the glass?

To mods: If this fits chemistry better, please move it.

I would favor clay over the glass; not because of any empirical evidence but by personal experience. I think that the original question refers to any rapid change of temperature, up or down. Once I was baking a potato & ham casserol in a pyrex (glass) dish. When I opened the oven door, a blast of cold air from my cooling duct hit it, and caused the dish to EXPLODE, sending shards of glass flying 15 feet away. Another time my clay pizza stone cracked for the same reason. No material is immune from thermal shock, but the clay I believe to be better.

Assuming that both the ceramic and the glass are not decorative bowls and are free from cracks or chips, either can stand up to 212 degrees just fine. However, if your bowls were in the fridge or freezer, you can have thermal shock issues that Dr. D talked about.