In reality, this comes down to what you like. Do you like a nice, cool and smooth hit? If so a low temperature is the way to go. If you like it hard and heavy, well more heat will help with that.
428 would be the perfect temp as all cannabinoids are vaporized at that temperature. We feel 450-500 is good. Remember the temperature reading is not perfect and is only measuring a thermister in the actual heating element.
Learn more about vaping temps here