The ice tray with very cold tap water will create ice cubes first.
When you put an ice tray in the freezer, the water inside begins to cool down and freeze. The process of freezing occurs when the temperature of the water drops below its freezing point (0 degrees Celsius or 32 degrees Fahrenheit).
In the case of the very cold tap water, the starting temperature is already quite close to the freezing point. The freezer's cold environment will further lower its temperature, and the water will freeze relatively quickly as it only needs to lose a few degrees of heat.
On the other hand, with the boiling water, its starting temperature is significantly higher than the freezing point. In order to reach the freezing point, it first needs to lose a substantial amount of heat to cool down. As the water loses heat, it will go through the temperature range where liquid water exists, but it's not yet frozen. Only after the water cools down to the freezing point will it start the process of freezing and form ice cubes.
So, while both trays will eventually freeze, the ice tray with very cold tap water will create ice cubes first due to its lower starting temperature.